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- 6. 河村雅人 从事物联网与机器人的研发 ， 工作内窑涉及 软件架构、 产目选定 ， 甚至还包括焊接 、 编 程等。 大摞结盟 曾参与过应用了机器人中间件和AR交E技 术的机器人服务开发， E见致力于物联网相机器 对机器通信领域， 以及与传感器中目：关的研发。 小林佑辅 致力于技术开发 ， 近年来尝试着把自己在数 据分析工作上的经验应用到技术开发中。 小山武士 负责安全技术开发 ， 现在热衷于开发设计可 穿戴设备安全性方面的应用技术。 富崎窗也 专注于开发那些用来解决社会问题的机器人 服务， 从事云机器人基础架构的研发以及服 务模型和应用方案的拟定。 石黑佑树 在大学和研究生时期专攻机器人专用中间件 的应用和机器人系统集成的研究。 进入NTT DATA后一 直追求与未来相关的主题 ， 如墓 于机器人和云的联动技术的植物工厂等。 小岛康平 致力于云机器人墓础架构的研发 ， 以及有关 物联网相机器人的技术开发 ， 力图在服务型 机器人的社会应用方面作出贡献。 封面插画： 山下以登
- 7. 国 ＼自美丽 ［日］ NTT DATA集团著 ［ 河村雅人大摞纯史小林馅辅小山武士寸 富崎管也石黑佑树小岛康平 」 丁灵译 ． ． 人民邮电出版社 北 京 II!mi:m 图灵程序 设计丛书
- 8. 图书在版编目 （CIP） 数据 图解物联网 / 日本NTT DATA集团等著； 丁灵译. -- 北京： 人民邮电出版社， 2017.4 （图灵程序设计丛书） ISBN 978-7-115-45169-9 Ⅰ. ①图… Ⅱ. ①日… ②丁… Ⅲ. ①互联网络－应 用－图解②智能技术－应用－图解 Ⅳ. ①TP393.4-64 ②TP18-64 中国版本图书馆CIP数据核字 （2017） 第054889号 内 容 提 要 本书运用丰富的图例， 从设备、 传感器以及传输协议 （MQTT） 等构成物联网的 技术要素讲起， 逐步深入讲解如何灵活运用物联网。 内容包括用于实现物联网的架 构、 传感器的种类以及能从传感器获取的信息等基础知识， 并进一步介绍了感测设备 原型设计所必需的Arduino等主板及这些主板的选择方法， 连接传感器的电路， 传感 器的数据分析， 乃至物联网跟智能手机/可穿戴设备的联动等。 此外， 本书以作者们 开发的物联网系统为例， 讲述了硬件设置、 无线通信以及网络安全等运用物联网系 统时会出现的问题和必备的诀窍。 本书适合那些想了解物联网的基础知识和整体情况， 或是今后要从事物联网和 机器对机器通信系统规划或开发的人士， 以及所有对物联网系统开发感兴趣的硬件 和软件工程师阅读。 ◆ 著 ［日］ NTT DATA集团 河村雅人/大塚纮史/小林佑辅/小山武士/宫崎智也/ 石黑佑树/小岛康平 译 丁 灵 责任编辑 傅志红 执行编辑 高宇涵 侯秀娟 责任印制 彭志环 ◆ 人民邮电出版社出版发行 北京市丰台区成寿寺路11号 邮编 100164 电子邮件 315@ptpress com.cn 网址 http://www.ptpress.com.cn 北京 印刷 ◆ 开本： 880×1230 1/32 印张： 9.75 字数： 291千字 2017年4月第1 版 印数： 1-3 500册 2017年4月北京第1次印刷 著作权合同登记号 图字： 01-2016-5336号 定价： 59.00元 读者服务热线： (010)51095186转600 印装质量热线： (010)81055316 反盗版热线： (010)81055315 广告经营许可证： 京东工商广字第8052号
- 9. 本书内容 近年来，机器对机器通信（Machine to Machine，M2M）和物联网 （Internet of Things，IoT）这两个关键词备受瞩目。不仅是计算机，物联 网还涉及智能手机和家用电器这些跟我们生活息息相关的物品和设备。 物联网的原理是从安装在这些物品和设备上的传感器处收集信息，并通 过互联网对其加以灵活运用。 本书面向那些想在系统开发中应用物联网的工程师，从设备、传感 器以及传输协议（MQTT）等构成物联网的技术要素的基础知识讲起， 逐步深入到如何灵活运用物联网。 要想应用传感器，除了传感器的知识以外，我们还需要掌握硬件和 软件的知识、用于分析传感器数据的知识等。本书内容包括用于实现物 联网的架构、传感器的种类以及能从传感器获取的信息等基础知识，并 进一步介绍了感测设备原型设计所必需的 Arduino 等主板及这些主板的 选择方法，连接传感器的电路，传感器的数据分析，乃至物联网跟智能 手机 / 可穿戴设备的联动等。这些都是工程师在运用物联网之前需要事 先了解的知识。此外，本书以作者们开发的物联网系统为例，讲述了与 硬件和无线通信相关的一些特有问题，设置设备的窍门以及网络安全 等，除此之外，书中还提到了一些运用物联网系统时会出现的问题和必 备的诀窍。 本书适合想要了解物联网的基础知识和整体情况，或是今后要从事 物联网和机器对机器通信系统规划或开发的人士，以及所有对物联网系 统开发抱有兴趣的工程师阅读。
- 10. 前 言 这是一本解说物联网的书。物联网整体服务的开发需要灵活应用传 感器和各类设备，本书就是为那些准备从事这种开发的硬件和软件工程 师编写的。 相信大家近来也经常听到物联网这个词吧。物联网是通过互联网把 我们身边的各种物品连在一起，并提供服务的一种机制。它可以给大家 的生活带来如同科幻电影一般的体验。 一方面，物联网利用的技术是以现有 Web 服务中使用的技术和互联 网为基础的。另一方面，为了了解传感器和各类设备的用途，我们需要 掌握一些相关的硬件及嵌入式软件知识。 Web 服务和互联网的知识是 IT 工程师的专长，而传感器和设备的 知识就是嵌入式工程师和硬件工程师的拿手好戏了。我们必须灵活应用 这两类工程师各自擅长的领域才能实现物联网。此外，物联网还会用到 数据科学家擅长的技术领域，即对设备所传输的信息进行分析的技术以 及机器学习的相关内容。 当然，如果这些工程师能把彼此擅长的技术聚合到一起，就能实现 物联网了。然而要是不理解对方领域的基础知识，他们就难以相互理 解，实现物联网也就非常困难。因此本书的写作目的就在于帮助大家， 即使在开始物联网项目时碰到了自己不懂的领域也不至于手足无措。 首先，我们将在第 1 章中总览物联网，然后在第 2 章中围绕 Web 服 务使用的技术，就物联网服务的实现方法予以说明。第 3 章会详细解说 设备开发中需要把握的重点，而第 4 章则以先进的传感器为题，为大家 介绍近年来取得惊人进步的自然用户界面（Natural User Interface，NUI） 和 GPS 等感测系统。第 5 章会为大家介绍一些运用物联网服务时的诀窍 和需要注意的地方。第 6 章到第 8 章则涵盖数据分析、可穿戴设备以及 机器人等跟物联网紧密相连的领域。 本书旨在帮助大家迈出全面了解广阔的物联网技术领域的第一步，
- 12. 目 录 第 1 章 物联网的基础知识 1 1.1 物联网入门……2 1.1.1 物联网……2 1.1.2 物联网的相关动向……2 1.2 物联网所实现的世界……3 1.2.1 “泛在网络”社会……3 1.2.2 “物”的互联网连接……4 1.2.3 机器对机器通信所实现的事……5 1.2.4 物联网实现的世界……6 蓬勃发展的标准化活动……8 1.3 实现物联网的技术要素……9 1.3.1 设备……9 1.3.2 传感器……13 1.3.3 网络……15 1.3.4 物联网服务……17 1.3.5 数据分析……20 第 2 章 物联网的架构 23 2.1 物联网的整体结构……24 2.1.1 整体结构……24 2.1.2 网关……25 2.1.3 服务器的结构……27 2.2 采集数据……28
- 13. VIII 目 录 2.3 接收数据……30 2.3.1 数据接收服务器的作用……30 2.3.2 HTTP 协议……30 REST API……31 2.3.3 WebSocket……32 2.3.4 MQTT……33 2.3.5 数据格式……40 图像、语音、视频数据的处理……43 2.4 处理数据……44 2.4.1 处理服务器的作用……44 2.4.2 批处理……44 2.4.3 流处理……47 2.5 存储数据……49 2.5.1 数据库的作用……49 2.5.2 数据库的种类和特征……50 2.6 控制设备……54 2.6.1 发送服务器的作用……54 2.6.2 使用 HTTP 发送数据……54 2.6.3 使用 WebSocket 发送数据……55 2.6.4 使用 MQTT 发送数据……55 事例：面向植物工厂的环境控制系统……56 第 3 章 物联网设备……59 3.1 设备——通向现实世界的接口……60 3.1.1 为什么要学习设备的相关知识……60 3.1.2 连通性带来的变化……60 3.2 物联网设备的结构……63 3.2.1 基本结构……63 3.2.2 微控制器主板的类型和选择方法……68 开源硬件的兴起……80
- 14. 目 录 IX 3.3 连接“云”与现实世界……80 3.3.1 与全球网络相连接……80 3.3.2 与网关设备的通信方式……81 3.3.3 有线连接……82 3.3.4 无线连接……84 3.3.5 获得电波认证……89 3.4 采集现实世界的信息……89 3.4.1 传感器是什么……89 3.4.2 传感器的机制……90 3.4.3 传感器的利用过程……94 3.4.4 放大传感器的信号……95 3.4.5 把模拟信号转换成数字信号……96 3.4.6 传感器的校准……98 3.4.7 如何选择传感器……100 3.5 反馈给现实世界……103 3.5.1 使用输出设备时的重要事项……103 3.5.2 驱动的作用……104 3.5.3 制作正确的电源……107 3.5.4 把数字信号转换成模拟信号……108 3.6 硬件原型设计……110 3.6.1 原型设计的重要性……110 3.6.2 硬件原型设计的注意事项……111 3.6.3 硬件原型设计的工具……114 挑战制作电路板！……115 3.6.4 原型制作结束之后……116 第 4 章 先进的感测技术……119 4.1 逐步扩张的传感器世界……120 4.2 先进的感测设备……120
- 15. X 目 录 4.2.1 RGB-D 传感器……122 4.2.2 自然用户界面……129 4.3 先进的感测系统……132 4.3.1 卫星定位系统……133 4.3.2 准天顶卫星……144 4.3.3 IMES……145 4.3.4 使用了 Wi-Fi 的定位技术……147 4.3.5 Beacon……150 4.3.6 位置信息和物联网的关系……152 第 5 章 物联网服务的系统开发……153 5.1 物联网和系统开发……154 5.1.1 物联网系统开发的问题……154 5.1.2 物联网系统开发的特征……155 5.2 物联网系统开发的流程……157 5.2.1 验证假设阶段……158 5.2.2 系统开发阶段……159 5.2.3 维护应用阶段……159 收益共享……160 5.3 物联网服务的系统开发案例……161 5.3.1 楼层环境监控系统……161 5.3.2 节能监控系统……164 5.4 物联网服务开发的重点……166 5.4.1 设备……167 5.4.2 处理方式设计……175 5.4.3 网络……183 5.4.4 安全性……185 5.4.5 应用与维护……192 5.5 面向物联网服务的系统开发……195
- 16. 目 录 XI 第 6 章 物联网与数据分析……197 6.1 传感器数据与分析……198 6.2 可视化……200 6.3 高级分析……207 6.3.1 高级分析的基础……207 机器学习和数据挖掘……216 6.3.2 用分析算法来发现和预测……216 6.3.3 预测……217 6.4 分析所需要的要素……221 6.4.1 数据分析的基础架构……221 6.4.2 CEP……224 6.4.3 Jubatus……225 分析的难度……227 第 7 章 物联网与可穿戴设备……229 7.1 可穿戴设备的基础……230 7.1.1 物联网和可穿戴设备的关系……230 7.1.2 可穿戴设备市场……233 7.1.3 可穿戴设备的特征……237 7.2 可穿戴设备的种类……239 7.2.1 可穿戴设备的分类……239 7.2.2 眼镜型……243 7.2.3 手表型……248 7.2.4 饰品型……250 7.2.5 按照目的来选择……253 7.3 可穿戴设备的应用……261 7.3.1 可穿戴设备的方便之处……261 7.3.2 消费者应用情景……262
- 17. XII 目 录 7.3.3 用于企业领域……265 硬件开发的近期动向……268 第 8 章 物联网与机器人……271 8.1 由设备到机器人……272 8.1.1 机器人——设备的延续……272 8.1.2 机器人的实用范围正在扩大……273 8.1.3 构建机器人系统的关键……274 8.2 利用机器人专用中间件……275 8.2.1 机器人专用中间件的作用……275 8.2.2 RT 中间件……276 8.2.3 ROS……278 8.3 连接到云端的机器人……280 8.3.1 云机器人……280 8.3.2 UNR-PF……281 8.3.3 RoboEarth……284 8.4 物联网和机器人的未来……287 后记……289 参考文献……291 作者……296
- 18. 物联网的基础知识 第1章
- 19. 2 第 1 章 物联网的基础知识 首先我们来了解一下学习物联网所需的基础知识。 物联网 大家在听到物联网时，脑海中会出现一个什么样的印象呢？ 物联网的英语是 Internet of Things，缩写为 IoT，这里的“物”指的 是我们身边一切能与网络相连的物品。例如您身上穿着的衣服、戴着的 手表、家里的家用电器和汽车，或者是房屋本身，甚至正在读的这本 书，只要能与网络相连，就都是物联网说的“物” 。 就像我们用互联网在彼此之间传递信息一样，物联网就是“物”之 间通过连接互联网来共享信息并产生有用的信息，而且无需人为管理就 能运行的机制。这样一来，就创造出了一直未能实现的魔法般的世界。 物联网的相关动向 ICTA 市场调查公司的 IDC（Internet Data Center，互联网数据中心） 调查结果显示，2013 年日本国内物联网市场的市场份额约有 11 万亿日 元，预测这个数字在 2018 年大约会增至 2013 年的两倍，即 21 万亿日 元左右。 物联网市场是由若干个市场形成的，包括作为“物”的设备市场， 掌管物与物之间联系的网络市场，还有运营管理类的平台市场，分析采 集到的数据的分析处理市场等（图 1.1） 。 A 信息、通信和技术三个英文单词的首字母组合（Information Communication Technology， 简称 ICT） 。——译者注（本书脚注均为译者注）
- 20. 1.2 物联网所实现的世界 3 基于数据分析结果来提供特定服务 的应用市场 ●分析 “ 物 ” 采集到的数据的软件市场 ●咨询市场 实现 “ 物 ” 的激活及认证 / 计费 / 通信管理的平台服务市场 通信基础设施 / 通信设备市场 通信模块市场 设备和嵌入式系统的市场 网 络 安 全 服务应用 平台 设备 网络 分析处理 图 1.1 物联网的相关市场 说起创建物联网市场的要素，那就要提到通信模块价格趋向低廉以 及云服务的普及。英特尔公司在 2014 年 10 月将一款名为英特尔 Edison 的单板计算机投入了市场。这款单板机在一个只有邮票大小的模块上搭 载了双核双线程的 CPU 和 1 GB 内存、4 GB 的存储空间、双频的 Wi-Fi 以及蓝牙 4.0。除此之外，微软还公布了名为 Microsoft Azure Intelligent Systems Service（Azure 智能系统服务）的解决方案，它负责用云技术实 现数据管理和处理，以及通信管理等功能。 此外，在平台、分析处理和网络安全等方面，针对物联网的产品和 服务也已经开始投入市场。物联网市场今后的重点在于跟熟悉各垂直市 场的从业者加强合作，积极提供试验环境以及开发贴近用户生活的服务 项目。 “泛在网络” 社会 在讲物联网所实现的世界之前，我们先从“连接网络”的观点来回
- 21. 4 第 1 章 物联网的基础知识 顾一下历史。 20 世纪 90 年代初，过去以大型机为中心的集中式处理逐渐向以客 户端服务器为中心的分布式处理转移。自 20 世纪 90 年代后期起，新型 集中式处理围绕着以互联网和 Web 为代表的网络形成了一股发展趋势。 这就是 Web 计算的概念。以互联网为媒介，人们可以轻松实现 PC、服 务器、移动设备之间的信息交换。 21 世纪初，一个名为“泛在网络”的概念开始受到人们的关注。泛 在网络的理念在于使人们能够通过“随时随地”连接互联网等网络来利 用多种多样的服务（图 1.2） 。近年来，通过智能手机和平板电脑，甚至 游戏机、电视机等一些过去无法连接到网络的“物” ，就可以随时随地 访问互联网。 Web 计算 人 泛在网络 Internet 移动 PC 信息 服务器 PC 大型机 Internet 移动 PC 信息 服务器 PC 大型机 电视机 平板电脑 游戏机 手机 Internet of Information （信息） Internet of People （人） 图 1.2 泛在网络可以让人们随时随地访问网络 “物” 的互联网连接 随着宽带的普及，泛在网络社会日益得到实现。此外，能搭载在机 器上的超低功耗传感器投入市场、无线通信技术进步等，都促使除了电 脑、服务器和智能手机等传统连接互联网的 IT 相关设备以外，各种各 样的“物”也可以连接互联网（图 1.3） 。以汽车、家用电器以及房屋为
- 22. 1.2 物联网所实现的世界 5 开端，近来，眼镜和手表、饰品这些戴在身上的“物”也连接上了互联 网并开始得到应用，如 Google Glass 和 Apple Watch。 泛在网络 人 Internet 移动 PC 信息 服务器 PC 大型机 电视机 平板电脑 游戏机 手机 Internet of People （人） Internet of Things （物） 移动 PC 服务器 PC 大型机 基础设施 建筑 图书 机器人 感测设备 家用电器 Internet 平板电脑 汽车 手机 生活用品 游戏机 医疗器械 电视机 农场 物 人信息 图 1.3 连接互联网的各种各样的“物” 形形色色的“物”都能与互联网相连，这一点大家都已经了解了。 那么这种“相连”会产生什么呢？它又是如何给人们的生活带来方便的 呢？下面，就来看看物联网带给我们的世界吧。 机器对机器通信所实现的事 在物联网的实现方面，近年来机器对机器通信等关键技术备受人们 关注（图 1.4） 。物联网和机器对机器通信在很多方面可以视作同一个意 思，但从严格意义上来说二者是不同的。机器对机器通信是不经人为控 制的、机器和机器之间的通信；也就是说，多数情况下它表示的是机器 和机器自动交换信息的整体系统。另一方面，物联网则大多含有给信息 接收者提供服务的含义，它比机器对机器通信的概念范围更广。
- 23. 6 第 1 章 物联网的基础知识 独立式住宅 办公大楼 农场 医院 / 诊所 政府机关 智能手机 零售业 自动贩卖机 汽车 / 电动车 道路 / 桥梁 工厂 / 仓库 交通 / 电动车 先进的交通系统 饮料 在线标定 设施监控 桥梁监控 工厂监控 远程维护 能源 能源管理 空调控制 农业 生长环境管理 医疗保健 看护 健康和疾病预防 防灾 测量水位 家庭自动化 终端管理 市场营销 购买行为追踪 数字标牌 机器对机器通信 图 1.4 机器对机器通信所实现的社会 泛在计算的世界是一个所有的“物”都内置计算机中，随时随地 可以得到计算机帮助的世界。而机器对机器通信支撑着泛在计算的世 界，并通过支撑社会的基础设施——智能社区和智能电网等形式逐步得 到实现。 此外，机器对机器通信不仅可以通过 3G 和 LTE 电路的信息系统实 现，还可以通过本地网络中的无线通信和有线通信来实现。 除了企业内的信息和互联网的信息以外，我们还能够灵活应用来自 机器的信息。这样一来也就掌握了现实世界中的情况变动，尤其是提高 了企业中的信息应用度。 物联网实现的世界 大家已经知道，我们可以借助机器对机器通信采集和积累信息，并 灵活运用从信息中分析出的数据来方便我们的生活。那么，如果在此基 础上把数百亿台设备都连接上物联网，又会如何呢？ 以前，人们通过让少数昂贵的工业机械通信，来实现对“物”的远
- 24. 1.2 物联网所实现的世界 7 程控制。今后，人们将更多地以低廉的价格大量生产面向用户的机器， 并让这些机器通信。也正因应用了从这些“物”中获取的数据，各种各 样的服务才如雨后春笋般涌现出来。此外，先进感测技术的普及实现了 人类对现实世界的掌握和预测，通过实时且海量地搜集人、物、社会和 环境的数据，也有望进行新型社会基础设施的构建，例如强化产业竞争 力、建设都市和社会制度、监测灾害等异常情况。 除了那些一眼就能看明白的设备，具有连通性（机器和系统间的互 联性和关联性）的设备也在不断地随处增加。物联网的趋势指的就是这 一现象。通过本章，我们再深入地看一下物联网所实现的是一个怎样的 世界。 1. 智能设备 2. 具备连通性的“物” 3. 网络 4. Web 系统 5. 数据分析技术 大家认为把这些因素组合到一起，将会产生出一个怎样的充满革新 性的服务呢？ 举个例子，市面上已经出现了很多叫作智能家居的设备，其用途是 控制智能住宅。飞利浦 Hue 是一款能通过 IP 网络来控制自身亮度和光 色的灯泡。Nest 是一种机器控制器，它能学习如何控制空调等机器以及 如何设定这些机器的目标值。如果把它们与 Web 系统和可穿戴设备等智 能设备组合在一起，还能实现由住宅主动根据人的动作和身体状况来调 整环境（图 1.5） 。
- 25. 8 第 1 章 物联网的基础知识 房屋 具备连通性的 “ 物 ” 空调 具备连通性的 “ 物 ” 灯泡 网络 具备连通性的 “ 物 ” 机器控制器 智能设备 可穿戴设备 网络 网络 云服务 数据分析技术 Web 系统 ④根据机器控制 器发出的控制信 号更改设定 ③根据人的身体 状况和感情状况向 空调和灯泡发出 控制信号 ①家用电器和可穿 戴设备被连接到网络 ②由可穿戴设 备通过语音等信息推 测人的身体状况和 感情状况 图 1.5 根据人体状况自动控制环境——以智能家居为例 可以说，当下的趋势之一就是不停留在单纯的控制层面，而是像 “凭借短距离通信实现自主控制和自动化”及“通过机器学习实现自动 判断”这样，给事物增添附加价值。 蓬勃发展的标准化活动 除 IETEA 、 3GPPB 、 ITUC 等标准化团体以外， 民间企业也围绕 物联网积极地开展了活动。 2013 年 12 月，在美国高通公司的支持下，家电厂商的横向 性物联网推进联盟 AllSeen Alliance 成立了。该联盟的意图在于越 过厂商这道高墙，规划一种统一规格，让冰箱、烤箱及电灯等所 有电器都能通过互联网实现协作。 A The Institution of Electronics and Telecommunication Engineers 电子与电信工程师 协会。 B Third Generation Partnership Project 第三代合作伙伴计划。 C International Telecommunication Union 国际电信联盟。
- 26. 1.3 实现物联网的技术要素 9 2014 年 7 月，在英特尔和三星的推动下，物联网联盟 OICA 成立了。该联盟旨在为物联网相关机器的规格和认证设立标准。 可想而知，今后物联网普及的关键在于各厂商是否采用这种 开放性规格。作为从事物联网的工程师，在选定产品时还得把这 种标准化动向考虑进去，这一点是重中之重。 要实现物联网，需要很多技术要素。除了传感器等电子零件和电子 电路以外，还包括 Web 应用中经常用到的技术，以及数据分析等。本书 将会为大家整体解说这些技术。个别详细内容在第 2 章及以后的章节中 会提到，这里我们先来总览一下本书将会讲解的全部内容。 设备 物联网与以往的 Web 服务不同，设备在其中担任着重要的作用。设 备指的是一种“物” ，它上面装有一种名为传感器的电子零件，并与网 络相连接。比如大家拿着的智能手机和平板电脑就是设备的一种。家电 产品、我们时刻戴着的手表以及伞等，只要能满足上述条件，就是设备 （图 1.6） 。 A Open Interconnect Consortium 开放互联联盟。
- 27. 10 第 1 章 物联网的基础知识 物联网服务 伞的开合 当前位置 网页浏览 佩戴者的 生命体征 电源的 开 / 关 互联网 图 1.6 与网络连接的设备 这些设备起着两个作用：感测和反馈。下面我们分别说明它们各自 的作用。 ◉感测的作用 感测指的是搜集设备本身的状态和周边环境的状态并通知系统（图 1.7） 。这里说的状态包括房门的开闭状态、房间的温度和湿度、房间里 面有没有人，等等。设备是利用传感器这种电子零件来实现感测的。 打个比方，如果伞上有用于检测其开合的传感器并具备连接网络的 功能，那么多把伞的开合状态就可以被检测到。利用这一点就能调查出 是否在下雨。在这种情况下，如果一个地区有多把伞打开，就可以推测 出该地区正在下雨。反过来，就能推断出大多数伞都合着的地区没有在 下雨。此外，通过感测设备周边的环境还能搜集温度和湿度等信息。
- 28. 1.3 实现物联网的技术要素 11 感测门的状态 感测的作用 感测周围的环境 向网络发送信号 网络 温度 湿度 光 门的开闭 是否上了锁 图 1.7 感测的作用 ◉反馈的作用 设备的另外一个作用是接收从系统发来的通知，显示信息或执行指 定操作（图 1.8） 。系统会基于从传感器处搜集到的信息进行一些反馈， 并针对现实世界采取行动。 反馈的作用 系统发出的指示 门的开闭 光的变化 “物”的 状态变化 温度和湿度 的变化 电源的开/关 上锁/开锁 更改设定温度 网络 图 1.8 反馈的作用
- 29. 12 第 1 章 物联网的基础知识 反馈有多种方法。大体分成如图 1.9 所示的 3 种方法，分别是可视 化、通知，以及控制。 请求 可视化界面 设备控制指令 推送通知 环境和设备的状态 发生改变 系统判断的结果会 显示在界面上 网络 可视化 网络 通知 网络 控制 显示感测结果界面和 设备管理界面 图 1.9 反馈的 3 种方法 比方说，用户通过“可视化”就能使用电脑和智能手机上的 Web 浏 览器浏览物联网服务搜集到的信息。虽然最终采取行动的是用户，不过 这是最简单的一个反馈的例子。只要把房间的当前温度和湿度可视化， 人就能将环境控制在最适宜的条件下。 利用“推送通知” ，系统就能检测到“物”的状态和某些活动，并 将其通知给设备。例如从服务器给用户的智能手机推送通知，使其显示 消息。近年来，Facebook 和 Twitter 等 SNS 社交应用就在贴心地向我们 的智能手机频繁推送朋友们吃饭和旅行的消息。如果你去逛超市时，推 送通知能告诉你冰箱的牛奶过了保质期，洗涤用品卖完了，这个世界岂 不就更方便了吗？ 利用“控制” ，系统就可以直接控制设备的运转，而无需借助人工。 假设在某个夏天的傍晚，你正在从离家最近的车站往家走，你的智能手 机会用 GPS 确定你现在的位置和前进的方向，用加速度传感器把你的步 速通知给物联网服务。这样一来，服务就能分析出你正在回家的路上，
- 30. 1.3 实现物联网的技术要素 13 进而从你的移动速度预测你到家的时间，然后发出指示调节家里空调的 温度并令其开始运转。这样当你回到家的时候，家里就已经很舒服了。 传感器 要想像前文说的那样搜集设备和环境的状态，就需要利用一个叫作 传感器的电子零件。 传感器负责把物理现象用电子信号的形式输出。例如有的传感器可 以把温度和湿度作为电子信号输出，还有的传感器能把超声波和红外线 等人类难以感知的现象转换成电子信号输出。 数码相机上使用的图像传感器也能把进入镜头的光线捕捉成 3 种颜 色的光源，并将其转换成电子信号。因此它也可以归在传感器的分类 里。传感器的种类如图 1.10 所示。关于这些传感器的种类和它们各自的 结构，我们会在第 3 章详细介绍。 能拍摄图像 能测量光的强度 能测量所在设备的 加速度 能感知磁场并 辨别方向 能测量温度 能测量湿度 图像传感器 光学传感器 温度传感器 湿度传感器 加速度传感器 磁场传感器 图 1.10 具有代表性的传感器的种类 通过传感器输出的电子信号，系统就能够获取现实世界的“物”的
- 31. 14 第 1 章 物联网的基础知识 状态和环境的状态。 人们很少单独利用这些传感器，通常都是将它们置入各种各样的 “物”里来加以利用。最近的智能手机和平板电脑就内置了很多传感器， 例如用于检测画面倾斜度的陀螺仪传感器和加速度传感器，采集语音的 麦克风，用于拍摄照片的相机，具备指南针功能的磁场传感器。 还有一种东西叫作传感器节点，它把传感器本身置入环境中搜集信 息。传感器节点是集蓝牙和 Wi-Fi 等无线通信装置与电池为一体的传感 器。我们把这些传感器连接到一种叫作网关的专用无线路由器来进行传 感器数据的搜集（图 1.11） 。 网关 发送遥感数据 配备 了传感器和 通信机器的设备 传感器节点C 传感器节点B 传感器节点A 融合遥感数据 图 1.11 传感器节点和网关 比如，在农场测量栽培植物的环境时，或是检测家里房间的温度和 湿度时，就可以利用这些传感器节点。除此之外，市面上还有各种各样 用于医疗保健的可穿戴设备，这些设备上装有加速度传感器和脉搏计， 人们可以利用这些设备管理自己的生活节奏和健康状况。 这样一来，物联网服务就能利用传感器获取设备、环境、人这些
- 32. 1.3 实现物联网的技术要素 15 “物”的状态。自己想实现的服务都需要哪些信息，为此应该利用哪种 传感器和设备，这些都需要我们仔细分析。 网络 在把设备连接到物联网服务时，网络是不可或缺的。不仅要把设备 连接到物联网服务，还得把设备连接到其他设备。物联网使用的网络大 体上分为两种：一种是把设备连接到其他设备的网络，另一种是把设备 连接到物联网服务的网络（图 1.12） 。 设备 设备 设备 把设备连接到其他 设备的网络 把设备连接到物联网 服务的网络 互联网 图 1.12 用于物联网的两种网络 把设备连接到其他设备的网络 无法直接连接到互联网的设备也是存在的。我们通过把设备连接到其 他设备，就能通过其他设备把这些不能连接到互联网的设备连接到互联网。 前面我们介绍的传感器节点和网关正是两个典型的例子。此外，还有通 过智能手机把可穿戴设备采集到的数据发送给物联网服务这一办法。 蓝牙和 ZigBee 是两种具有代表性的网络标准。它们是用无线连接 的，利用的通信协议也是固定的。这些协议的特征有采用擅长近距离通 信的无线连接、低功耗、易于嵌入嵌入式设备等。 要把设备连接到其他设备，除了 1 对 1 之外，还可以采用 1 对 N、
- 33. 16 第 1 章 物联网的基础知识 N 对 N 的方式连接。特别是 N 对 N 连接的情况，我们称这种情况为网 状网络（图 1.13） 。 接管其他设备的通信 1对1连接 接管通信 合计多台机器的数据， 接管通信 1对N连接 聚合数据， 减少连接到系统的 客户端数量 采用网状连接的方式提升 通信的距离， 减少故障的 发生 N对N连接 利用未故障设备通信 图 1.13 设备之间的网络连接 有一种与网状网络对应的通信标准，名为 ZigBee。通过采用 N 对 N 的通信方式，设备可以一边接管其他的设备，一边进行远程通信。除此 之外它还有一个优点，那就是即使有一台设备发生故障无法通信，其他 设备也会代替它来执行通信。 关于上述设备的通信规格我们会在第 3 章讲解。 把设备连接到服务器的网络 把设备连接到物联网服务的网络时，会用到互联网线路。3G 和 LTE 等移动线路最为常用。 除了现在 Web 服务中广泛使用的 HTTP 和 WebSocket 协议以外，还 有一些专为机器对机器通信和物联网而产生的轻量级协议，如 MQTT
- 34. 1.3 实现物联网的技术要素 17 等。关于该协议，我们会在第 2 章进行详细说明。 物联网服务 物联网服务有两个作用：一是从设备接收数据以及发送数据给设备； 二是处理和保存数据（图 1.14） 。 物联网服务 设备 发送数据 发送数据 接收数据 接收数据 数据 数据 数据 数据 执行与设备之间 的数据交换 处理和保存 保存到数据库 根据接收到的数据 进行判断 图 1.14 Web 系统的作用 我们来具体看一下这两个作用。 数据交换 通常的 Web 服务会根据 Web 浏览器发送的 HTTP 请求发送 HTML， 然后用 Web 浏览器显示。物联网服务则不采用 Web 浏览器，而是接收 从设备直接发来的数据。设备发来的数据内容包括设备搭载的传感器所 采集到的信息，以及用户对设备进行的操作。设备和物联网服务的通信 方法大致分为两种：同步传输和异步传输（图 1.15） 。 在同步传输的情况下，设备发送数据时会把数据发送给物联网服 务。接下来直到物联网服务接收完数据之前，不管设备向物联网服务发
- 35. Discovering Diverse Content Through Random Scribd Documents
- 36. At a very little distance from this church is a circular building, which has had the name of a Temple of Bacchus, on the very equivocal evidence of a sarcophagus of porphyry sculptured with the vine, now removed to the Vatican, and of some mosaics on the walls, relating also to the vintage. Other writers maintain that it was a baptistery erected by Constantine for the baptism of his sister and daughter, who are said also to have been buried here. The account is not improbable, as we have many instances of ancient baptisteries of this form, but some uncertainty seems to be thrown upon it, by its occupying a distinguished and symmetrical position, in a large oblong area, circular at one end, or perhaps at both, which has been called a Hippodrome, and which does not seem exactly suitable for a mere court to this building. All the external ornaments have disappeared; internally, we have a dome resting on twenty-four columns, which are placed in pairs on the radii of the circle, and surrounded by an aisle. Twenty of these columns are of gray granite, and four of red. The capitals are Composite, not very good, but evidently, as well as the columns, the spoils of some more ancient building, except one or two, which serve to shew the incompetency of the artists of the time of Constantine. The columns support a clumsy entablature, from which spring the arches; at a considerable space above these, is the dome. The effect is not good, but I do not think we can conclude any thing from it against this mode of arrangement, though the management of the radiating vaults supported on the columns, and larger externally than towards the centre, will always be a great difficulty. The columns here are too small, and too far apart, and not beautiful in themselves, nor in their bases and capitals. In adopting such a disposition, the detached entablatures are certainly to be rejected, and the small arches should spring, either from a mere architrave, or immediately from the capitals; and it is probably better to make the dome spring from the same point without any intervening drum, and to let the arches groin into it. The Church of San Lorenzo was originally built by Galla Placidia, but restored from the foundations by Pelagius the Second, before
- 37. 590. This church, whether of Pelagius or of Galla Placidia, was similar in form to that of St. Agnes, which I have already described to you, but Adrian the First, about 772, stopped up the old doorway, and took down the tribune, to join the old building to a new nave which he erected; thus completely reversing the church, and placing the altar before the ancient entrance. To this period I believe we are to refer the porch, though that may have been something later, as its frieze, with circles of mosaic work, nearly accords with that of the cloisters of St. John Lateran, and St. Paul; but the cornice, which consists of only a Welsh ogee, is rather in a singular style; and the ornaments, composed of bulls’ heads and palm trees, though not beautiful, are deeply and cleanly cut. The bases are Corinthian, and all alike. The capitals also are all of the same form, but they are badly worked, while the shafts are well executed. The nave has on each side eleven columns of Egyptian and oriental granite and cipollino, with Ionic capitals, differing in size, drawing, and workmanship. Pliny relates that Saurus and Batrachus, two Spartan architects, were employed by the Romans in the time of Augustus, to erect a temple, and not being permitted to inscribe their names on the building, they sculptured a lizard and a frog (which in Greek are called by the same names as these architects) on one of the capitals, to commemorate their exertions. On a capital in this nave, we find these animals engraved. The style of ornament and execution found in them, indicates rather the period of the erection of the porch, with which it nearly corresponds, than the time alluded to by Pliny; but the coincidence is remarkable. The most interesting, as well as the most ancient part, is the present choir, where we have ten ancient columns of considerable size, and very beautiful workmanship; though the excellence of the proportion is not now easily perceived, as a considerable part of them is buried. Two of these are of Greek marble, with Composite capitals; the rest are of a white veined marble, with beautiful Corinthian capitals. The latter perhaps formed part of the peristyle of an ancient temple, and are still in their original places. The entablature is made up of fragments, among which we trace pieces
- 38. of a door jamb with a rich and bold scroll; but the finest are parts of a small frieze, and they are very beautiful, but there is not the most trifling fragment corresponding with the columns. In the gallery above, there are twelve smaller columns, also antique. From this church is an entrance to extensive Catacombs. I did not enter them, for one thing of the sort is enough; and I had visited those at St. Sebastian. We will now proceed to some other churches, which, though likewise called basilicas, have neither originally had a transept, nor yet two stories of side aisles. Of these, by far the largest and most magnificent is that of Santa Maria Maggiore, which indeed in every respect is one of the finest churches in the world, both for the beauty of design, and the perfection of materials. The outside however, which is a work of the seventeenth and eighteenth centuries, does not deserve this praise; and it is remarkable, that in all the experiments the Romans have made in architecture, and the magnificence with which they have executed their undertakings, they have never hit even upon a moderately good design for the outside of a church. The front is contemptible; the back erected under the direction of Rainaldi, has considerable merit, and the character of a public building, but not of a church; but I am running into description before I have given you any sketch of the history of the edifice. The Church of Santa Maria Maggiore was erected by Giovanni Patrizio, and by the Pope St. Liberius, in consequence of a vision, and of a miraculous shower of snow, which fell on the spot on the 5th of August, and marked out precisely the plan of the building. It was dedicated in 352, and rebuilt in 432 by Sixtus the Third. This rebuilt is a vague term, and as the fall of snow is probably, like so many other stories of the Roman church, an invention of the middle ages, it will give us no reason to suppose that the original distribution was exactly preserved. In 1189, Nicolas the Fourth erected the tribune, and adorned it with mosaics. The present front was added by Benedict the Fourteenth, in 1741; at which time not only all the internal finishings were renewed, but the columns of the
- 39. nave were repolished, and reduced to one size and length, and uniform Attic bases, and Ionic capitals, were applied to them. Paul the Fifth erected in front, the only remaining column of the great hall of the temple of Peace, and placed upon it the bronze statue of the Virgin. Sixtus the Fifth displaced two of the northern range of columns to make a larger opening to the chapel which he erected; and Benedict the Fourteenth, in 1741, made a similar interruption in the opposite range, to form a correspondent opening to the chapel of Paul the Fifth; the back was erected under Clement the Tenth, about 1670. Internally, a single row of marble columns on each side divides the nave from the side aisles. These columns sustain a continued entablature, but they are here, as in so many other places, too small in proportion to the rest of the building, and the range of pilasters over them consequently too high. The general proportion of the room is perhaps a little too long and a little too low. In a design of this sort there must always be a difficulty in keeping down sufficiently the upper part, for it is in that, that the windows must be placed, and a considerable space must occur between the windows and the columns, in order to admit the roof of the side aisles. Another fault in this church arises from a comparatively recent alteration, interrupting the perspective of the ranges of columns, by arched openings into the two principal side chapels. The nave is above 50 feet wide, and about 280 feet long, and except for this interruption, exhibits an unbroken range of parts, all uniting into one rich and harmonious design. I hope you always keep in mind in considering these dimensions, that the nave of our St. Paul’s is but 41 feet wide. The side aisles are vaulted, which is bad; a continued vault will always look too heavy for columns; and besides, it does not correspond with the flat ceiling of the nave. This ceiling is in five panels in width, without irregularities, nobly disposed, and with a richness of carving and gilding well suited to its character. The Chapel of the Presepio (that of Sixtus the Fifth) is spotty, from the injudicious disposition of its marbles and gilding. The other chapel is less enriched, and on that account more beautiful; both are
- 40. very fine chapels, each of them having the form of a Greek cross, with very short arms. One other chapel in this church deserves attention; it is a simple parallelogram with Corinthian pilasters, the whole face of which is repeated at each angle. The architecture and the painting of the altar-piece seem to come from the school of Michael Angelo Buonarotti. At the Church of Santa Sabina on the Aventine, you may see a great stone, which the Devil in a passion flung one day at St. Dominic. You are also shewn a chapel which the saint used as an oratory, and an orange tree planted by him six hundred years ago; but perhaps you do not care much about these things. The usual entrance is on the side, by a little portico of four columns, two of which are of a very dark granite, or perhaps I should say sienite, for they are chiefly of hornblende, but one has a vein of red, and the other of light-coloured granite. In the capitals here, and in those within the church, the divisions of the leaves are not cut through the marble, but merely worked in relief, the outline of the undivided leaf being preserved. The bases are Corinthian, and as the apophysis of the column is very large, the small mouldings of this order look trifling. Internally, the nave is formed by twenty-four fluted marble columns, with Attic bases, said to have been taken from the temple of Diana, but I much doubt if the capitals of these belong to the building mentioned by Horace. As there was also a temple of Juno in the neighbourhood, the columns of the porch may have belonged to that. The columns of the nave support arches, and there is no entablature; indeed it is quite clear, that there ought never to be both, although Brunelleschi was of so different an opinion, that in such cases he made use of two entablatures, one in fragments, and one continued; and placed his arches between them. In this church also is a beautiful marble door-case, probably belonging to the same edifice as that from which the columns were taken. The ornamented face is not exposed in the church, but in a hall, which forms a communication between it and the cloisters; and in this hall are small columns with twisted flutes. It is difficult to say precisely when
- 41. this fancy began; but in small ornamental objects, it is doubtless of great antiquity. We may observe in the present day, that an architect gives himself more licence in small edifices, and in internal decorations, than in the more solid construction of large buildings; and it has always been so. Fancies in ornament please on a small scale, before they are generally adopted on a larger. The cloisters of this church are surrounded by single and coupled columns placed alternately, and supporting small arches, as in those of St. Paul and St. John Lateran. I say nothing of the history of this church, for in fact, the accounts we have of the construction of many of these edifices, is even more alike than the buildings, and you can seldom determine the date of any part with confidence. Our next object will be St. Clement’s, where I shall conduct you into the church by the principal and regular entrance, and through the court, a way at present seldom used. The first object is the Prothyron, where four granite columns support two corbels; upon these is an arch advancing beyond the columns, and over the arch a pediment. There is a little antiporch of the same nature, at the church of Santa Maria in Cosmedim. It is perhaps of the time of Adrian I., who restored this church in 772, but the original foundation of the building is attributed to the time of Constantine, and in 417 Celestius was condemned in it by the Pope St. Zosimus. You will observe that a large portion of the earlier popes were saints, though in later times this is seldom the case. From the Prothyron we pass into a court 58 feet long, and 48 wide, surrounded by porticos, which are supported on three sides by small granite columns. As a court, the dimensions are small; yet it seems a separation between the church and the bustle of the world, and is extremely pleasing in architectural effect. I do not mean in this church in particular, but as to the general idea. It appears that the width of the court from wall to wall never much exceeded that of the church with its side aisles, and it is probably much better that such should be the case. A small space makes the principal building look large; besides a small court evidently belongs to the church; a large one becomes an opening in the city. Leaving this court you enter the church, the nave of which
- 42. is formed as usual of plundered columns of different materials; and in the nave is the circuit in marble of the ancient presbytery, with its two pulpits; and the altar and apsis behind it, just as it was left in the twelfth century, when Cardinal Anastasius, under Pope Honorius the Second, restored the building, and had the apsis ornamented with mosaics. Somewhat of a similar presbytery, and in particular the two ambones, or pulpits, is also observable in San Lorenzo, but this is the most perfect example. It is said by Uggeri to be suited to the Greek ritual. I do not know why, or what differences the ancient Latin ritual would have required. Some authors I find apply the term ambo not to the pulpit, but to the whole of this enclosure for the presbytery; I do not pretend to decide which is right. You will think these basilican churches will never come to an end, but I must still trespass on your indulgence for a short description of two or three more. In that of San Martino de’ Monti, otherwise St. Martin and St. Sylvester, are twenty-four columns of different marbles, which have been all reduced to one size; but the capitals are not all alike, and some of them are gilt; they are said to have been brought from Adrian’s villa at Tivoli. The part above the order is too high in proportion, as is perhaps the case in all the basilican churches; but on the whole it is a very handsome church, and well worth visiting for its architecture alone. It is not however by this that strangers are principally attracted; the walls are adorned by the fresco landscapes of Gaspar Poussin, with figures by Niccolò. They are much damaged, and the colours have probably changed; perhaps they never were very good, yet they merit an examination. Here is a very handsome modern chapel, with a semidome well ornamented with ribs diverging from the centre. Another source of interest at this place is a subterraneum, said to have formed part of the baths of Trajan, afterwards to have been used as a church by St. Sylvester, who was made Pope in 314. It is sometimes added, that the baths of Trajan formed an appendage to those of Titus, and that St. Sylvester used this crypt in a time of persecution: two things hard to be believed. But at any rate these
- 43. high gloomy vaults exhibit some fine picturesque effects. There is no architecture in them, and nothing remarkable in their construction. In the Church of Santa Pudenziana the old columns are built up into niches in as ugly a manner as you can conceive; but it contains the relics of three thousand martyrs, and it is perhaps to correspond with this number, that we see on its walls, for those who visit it, an indulgence of three thousand years, and the remission of a third part of their sins. “Visitantes hanc ecclesiam, singulis diebus consequantur indulgentiam trium millium annorum et remissionem tertiæ partis peccatorum suorum.” I ask sometimes how long purgatory lasts, and what people do when they are discharged from it; but I cannot get any satisfactory information. The Church of Santa Prassede (a lady) is more famous for the rosso antico employed in its steps, than for its architectural merit. The effect, such as it was, has been spoilt by the arches thrown across the nave. Santa Maria in Domnica has a front erected by Raphael. The design is graceful, and the lower arcade well proportioned, but the upper part is not so well managed. Internally, some small figures on the frieze by Giulio Romano demand as much attention as the eighteen columns of black and green granite, which Manazzale mentions. In front of this church, stands on a pedestal, a marble model of a boat, but its date is rather uncertain. It was placed by Leo X. in its present position. In the portico of the Church of San Giorgio in Velabro are four small columns, one of granite, two of marble, and one of cipollino; the latter alone corresponds with the capitals, which are all alike, of the Ionic order, with larger volutes than is usual in the fragments remaining at Rome, of good general proportions, but not good in the detail. The doorway exhibits nearly the whole width of a frieze, the moulding and upper face of an architrave, and the corona and upper members of a cornice, in a bold and good style, resembling in character the remains we have in the church of Santa Maria in Cosmedim. The inside is not very easy of access, and contains little to reward us when we have procured admission, for mere antique
- 44. columns, and even handsome ones, are too common in Rome to obtain much attention. The tower, which is an edifice of the eighth century, being erected under Pope Zacchary, stands very insecurely on part of the arch of the goldsmiths, and one angle seems almost to rest on the edge of a single slab of marble. I pointed out this circumstance to a lad who was preparing the church for the festa. “Well, then,” said he, “I suppose the first earthquake will throw it down.” I replied, that such a result was extremely probable. “Well, it does not signify, I dare say there will be nobody here.” This tower, though far from beautiful, merits a more particular description, because it is of a style very common in Rome, and its date is well ascertained. The lower part is entirely plain, excepting the small moulding which terminates it, and is nearly hid by the body of the church. Above, there are four nearly equal stories, each crowned with a cornice, of which the uppermost is the largest; the lower of these has three recesses on one side only. The next has had three arches on each side, but they are now filled up; the third has likewise three arches, and these are still open. The upper has also three arches on each side, but these, instead of being separated by square piers, are divided by two columns, each of which supports a corbel immediately under the springing of the arch. The diameter of the column is very much less than the thickness of the wall, perhaps hardly above one third, so that the arches considerably overhang their supports. This fashion seems to have been widely spread, and to have lasted long, for the examples are very numerous at Rome and elsewhere. It would be difficult to determine how long, but I suspect some of them are as late as the eleventh century. When it was rare to build any thing of consequence, the desire of distinction did not require the frequent alteration of design, which takes place when more is executed; and architecture seems to have changed its type but little from the fourth or fifth, to the beginning of the eleventh century. “But dinner waits, and we are tired; Said Gilpin, so am I.”
- 45. I LETTER XXVII. LIVING AT ROME—MODERN CHURCHES. Rome, March, 1817. am going, I flatter myself, to satisfy you to the utmost, by giving the most minute detail of my Roman life. You will find it not so different from the manner of living in London as perhaps you expect; for in fact, the Romans are very much the same sort of beings as ourselves, and eat and drink, and have the same affections and appetites as the English. I will add, that the national character in both is pride, and not vanity; that they are rather reserved, and feel more than they shew: added to which, they finish their buildings as we do, and do not leave them half done, as in France, and many parts of Italy; but then they undertake them on a much more magnificent scale; and I believe, after all that has been said of the degeneracy of the modern Romans, that if their political institutions were favourable, they would have spirit to undertake, and resolution and perseverance to carry them through the greatest enterprizes. I will not enter into this subject till I have seen more of them, but relate those things which more nearly concern myself. In the first place, my lodgings consist of two good sized rooms, the largest of which is nearly thirty feet long on one side, but is very much out of a square, and as I have already told you, overlooks half Rome. They are both paved with bricks. The landlady offered me a mat for the whole room, but I was afraid of the fleas, and contented myself with one or two small pieces to put my feet upon. A small wood fire, which costs about 1d. per hour, serves to keep me warm in the
- 46. mornings and evenings. The sun would perform that office in the middle of the day, but I am then seldom at home. The bed, as usual in Italy, is large. Some boards, about six feet long, or a little more, are laid on two iron stands. On these is placed a great bag filled with the leaves of Indian corn, and over this two thin mattresses; of course there are no bed-posts, or hangings, or any thing of the sort; and this is the usual disposition of the beds in Italy, at least of those in common houses, and not intended for shew. The other furniture consists of a large press, which contains my clothes, and some books; a writing-desk, with drawers below; a square table; a smaller oval one; two side-tables against the wall; a straw couch; one large elbow-chair, and thirteen others. The chimney piece is made out of a piece of Greek marble. For fifteen hundred years the masons of Rome have been using up their old materials, and they are not yet exhausted. I apprehend, that during that period, hardly a single piece of new marble has been brought to Rome except for the use of the sculptors. And now, having given you an exact description of my lodgings, I will proceed to as particular an account of one day’s employment, from which you may judge of the rest. I rise about seven, or according to the Roman reckoning at the present moment, at 13 o’clock, at which time my attendant Leopold comes in, and brushes my coat, and blacks my shoes, all which is done in the room, for he never thinks of going elsewhere to perform these operations; he also makes the bed. This Leopold pays six crowns per month for his board and lodging in the house, and makes what he can of serving the lodgers, and in the evening attends the lady of the house to pay visits, or go to the theatre, not as a servant, but as a companion. Afterwards he brings me my breakfast of coffee and milk, which I always drink from a tumbler, and while I am eating it, he stops to relate to me various stories and opinions. Among other things he prides himself on being a Tuscan, not a Roman, complains of the bad government of Rome, and says priests are not fit for governors. Then he tells me, that he had been a soldier for some years, but always with some authority, and never as a mere private, that he
- 47. liked the employment very much, but was obliged to leave it on account of his being exceedingly short-sighted. His brother is a parson of some parish, (Parocco) and had been tutor in the family of the queen of Etruria. Leopold complains, that in his present employment his short-sightedness is very inconvenient. I asked him why he did not use spectacles; but he assured me they would make his sight worse. “Why,” said he, “a little while ago I saw a man with spectacles tumble down the steps of the Trinità. What, said I, could your spectacles help you to see no better? ‘Oh,’ replied the other, ‘the spectacles are of no use, I only wear them to be in the fashion; in England every body wears spectacles;’ but now,” adds Leopold, “I see a great many English, and it seems they do not wear spectacles.” He then proceeded to tell me, that he thought my Italian master could not be a good one, because he had spent a great part of his life in the country, and therefore could not naturally speak the language well; and that he had since been employed in various ways, none of which had succeeded, and that this must have prevented him from studying it; he would consequently neither be able to chuse the best and most elegant expressions, nor to pronounce correctly. Thus, you see my shoe-black is a man of various accomplishments, and is moreover quite a gentleman; for though he does not mind what he does within doors, he would not on any account be seen employed in any servile occupation without. Moreover, on the last day of the carnival, he would not by any means go on to the Corso on foot, because it was not genteel. After breakfast I usually employ myself a little while at home in drawing or reading, and then walk to the Campo Vaccino; here the forzati, i. e. the criminals condemned to hard labour, are employed in making excavations to expose for examination the antiquities of the place, and in some situations they have reached the old pavement thirty feet below the present surface. I continue my walk along the Via Sacra, and a parcel of children surround me, begging for half a bayoc. A little farther, a grinning little chit, looking quite fat and saucy, comes to tell me he is dying of hunger. However, there is in other cases plenty of the appearance, and I doubt not of the reality
- 48. of extreme misery. The harvests of wheat and maize, and the vintage, have been very deficient throughout Italy. I then walk into the Coliseum, and while drawing there, a soldier comes to me, a young lad of perhaps sixteen or seventeen years old, and tells me that he is obliged to serve three years; that he wished to procure a substitute, but was not permitted. Afterwards, he adds, that they are badly off under the pope, as their pay is only 3½ bayocs per day, and after some farther conversation, concludes with asking me for some money to buy brandy. I reply, that he would be much better without it; he then asks for something to buy bread, and assures me, that if I would not give him any, he must go to bed supperless. Afterwards, I return to my own dinner at a trattoria; these are not very good in Rome, but a person who is not fastidious may do very well. I begin with maccaroni and powdered cheese. The Italians eat this under the name of Parmesan, with their soups, and with vegetables, as well as with maccaroni, and the Romans have a favourite dish called gnocchi, which seems to consist of pieces of batter-pudding sprinkled with Parmesan, and eaten with sugar and cinnamon. As in France, they change your plates frequently, but give you only one knife and fork for every thing. On my return, the maid, for there is an old woman in the house, though the man makes the beds and dusts the chambers, wishes me a good evening, and desires to know at what hour she will have supper; for you know the Italians use the third person, and the she stands for vos signoria, your worship: they consider it very rude to say you to a superior, but I say you to them, for if I were to answer in the same manner, they would think I was laughing at them. By supper the old dame means tea; and I tell her to bring it at two o’clock, for the evening bell now rings at six. During the tea she usually has something to say to me, as Leopold had in the morning. Sometimes I go into society, or to the theatre, but not often, and now during Lent, all the theatres are shut up: and so ends my day. I went on twelfth day to hear a play which was acted by the children of the Orphan School. The subject was the adoration of the wise men, and the wrath of Herod. The stage was so small, that a
- 49. well grown boy appeared a giant. By whom the subject was reduced to a dramatic form I do not know, but his principal effort was in the character of two servants, whose wit, or blunders, formed great part of the entertainment of the evening. In the last act we are introduced to where the Saviour lies, not in a common stable or manger, but one resplendent with clouds and glory, and God the Father in the distance. It was really a very pretty scene in itself, however absurd as applied to the subject it pretended to represent. At this point, an Italian priest called out to another who happened to have his hat on, “Capello, signore, capello, signore, signore, vi è il bambino.” This notion of finding in the theatre a place of worship, was strangely at variance with all my English notions and feelings. I have said nothing about the Carnival, the observance of which is a custom too different from any of ours to be entirely neglected. The whole term lasts six weeks. I do not know if all the period ever used to be filled up with these vagaries, but the time now allowed for the reign of masking and folly is only eight days. These were preceded by a severe edict against carrying any weapon. The punishment for this offence is to be six years in the galleys; for drawing it, twelve years; for striking a person, eighteen years; for wounding him, confinement for life; for killing him, death. Premeditated assassinations are not, and perhaps never have been common at Rome; but when the common people quarrelled, and got into a passion, they sometimes used to stab each other. They are indebted to the French for the correction of this evil. The carrying the long sharp knives, which used to be the instrument of such assassinations, was declared to be immediate death, and it is said that no less than nineteen persons were shot the day after this law was promulgated; the following day two more, and afterwards now and then a straggler, but the habit was effectually broken: it seems a terrible remedy, but it was also a terrible disease. Confinement to real hard labour would perhaps have effected the cure, but more slowly, and the Roman police has yet no correct idea of this. The edict above mentioned also enjoined that no person should be masked except from the sounding of the bell of the Capitol, to that
- 50. of the Ave Maria, that is, from half past one to half past five. There are masked balls on some evenings, about which the edict says nothing, but every body understands that this is permitted. The edict also determines the size of the sugar-plums (which by the by are little pellets of whitening or plaster,) with which persons might be pelted without offence. At about four o’clock, people assemble on the Corso, and the rich parade up and down in their carriages; as indeed they do throughout the winter, though it does not seem a very pleasant ride. Close against the houses is a line of people sitting or standing, and where the street is wider, a row of chairs, or perhaps two rows of benches supported on scaffolding. Where this is the case, the front of the scaffold is usually adorned with old tapestry, and old tapestry is also hung out of the windows. Next to these is the stream of carriages, going up on one side, and down on the other; and in the middle a confused mixture of people, passing some one way and some another, interrupted now and then by the horse, or foot soldiers, parading up and down the streets. About a quarter before five, a gun sounds, as a signal for all carriages to go off the Corso, and at five, those which still remain there are turned off by the soldiers into the nearest streets. A rope is then stretched across, at the spot where the Corso opens into the Piazza del Popolo, and the horses are led up close to it. They have bits of tin hanging about them, and balls with pins to knock against their sides, and excite their speed as they go along. It is said that blisters are previously applied, to make the parts more tender. At a quarter past five, the rope is dropt, and off they start. The race is merely once along the Corso, and therefore is only an affair of a few minutes on the whole, and for any individual spectator hardly of half a minute. There is no time for betting, and I think this is one reason why the English are so generally dissatisfied with these races. The continued interest of our own races warms up the feelings, and produces a mental excitement, which such contests as these could never reach, either with or without riders, or with bad or good horses. After the race, carriages are again admitted on the Corso, but they soon disperse, and at the Ave Maria all is quiet again. The first day was very dull, with very few masks, and no humour. On the following
- 51. days the scene became more lively, especially in Giovedì Grasso. A great many men had female masks and dresses, and several women were dressed as men. The principal amusement seemed to be in the female masks, mobbing the unmasked gentlemen, and in pelting all their acquaintances with the so called sugar-plums. Some seemed to pelt every body, but I believe these were principally English. A party of students of the Neapolitan academy went about with a drawing- board and crayons, and affected to take portraits; when you looked at their production there was an ass’s head. Another party, consisting of French students, personated armed knights on horseback, and performed their gambols very well. After the Ave Maria, the theatres begin. There is plenty of time for every one to change his dress, but a large portion choose to preserve them, though all are obliged to abandon their masks, and the playhouses consequently present a most ridiculous scene. Before the gay time of the Carnival began, we had some very good acting, but during those mad days Pulcinella was pushed into every thing. This Pulcinella talks Neapolitan, and I lost many things which appeared to delight the audience; but most of the replies which I could comprehend had very little wit, though they excited a great deal of laughter; the barbarous language and pronunciation were more than half the jest. I went one evening to the masked ball or festina, which is given in a theatre not used at present for any other purpose: there were three parties of dancers, but the rooms were so crowded, that there was hardly space for them; a large proportion of the company was without masks: there was not much wit, but a good deal of cheerfulness and good humour. The entertainment was to begin at half an hour, and end at five, i. e. from six o’clock to half past ten; accordingly before eleven, the attendants began to put out the candles, and a file of soldiers gradually advancing, swept the place. There is no city where despotic authority assumes so undisguised a form as at Rome; where power, and not law, is so apparently the ruling principle; but perhaps we might not be the worse for it, if some of our public amusements were limited in as peremptory a manner. The masked ball on Friday night did not begin till after
- 52. midnight, in order not to disturb the religious observances of the day: the same rule was observed on Sunday, but I did not go to either. On the evening which closed this period of license, we had a new scene. It is the practice here, for the mourners at a funeral to carry lighted wax tapers; and on this evening, after the races, almost every body carried lighted tapers to celebrate the funeral of the Carnival; the street was crowded, the windows and balconies were all full of people, and everywhere we saw abundance of these candles; some persons carried them upon sticks, some stuck them upon their hats, others in the noses of their masks, but most were carried in the hand, and many persons had six or eight tapers twisted together to give a stronger light. Part of the amusement consisted in a mutual endeavour to blow out each other’s lights; the whole was very gay and splendid, and indeed the best thing in the carnival; but it seemed rather premature, as after that there was a masked ball, and after the ball, midnight suppers, where good catholics stuffed themselves as full as possible, to prepare for their long abstinence in Lent. In this year their holy father has spared them the mortification of abstinence; and as fish is dear, and the people very poor, he has granted a general dispensation to eat meat, except on Friday and Saturday. It is always a difficult thing to hear, or learn, good Italian in Italy, for the provincialisms extend to all ranks, and the inhabitants of one city are continually turning those of another into ridicule. It is true that in many places they speak their own provincial dialect to one another, and the Tuscan or Italian, when they converse with those who are not of the same province. “When these Bolognese chatter to one another,” said a Roman gentleman to me at Bologna, “I do not understand a word of what they say.” Yet some peculiarities will creep into the conversation, even when they think they are speaking the purest Tuscan. In spite of this, companies of dramatists go about from city to city, through the whole country, representing the same plays, with precisely the same words in each. It occurred to me, that these actors must thus get rid of all their own provincialisms; that they must study their language, and would probably understand it;
- 53. and moreover would be able to point out the usual defects of each place. I will confess however, that I have heard upon the stage, cielo pronounced as an Englishman would pronounce, shailo, and occhi with the ch like our ch in church. This was not favourable to my theory, but it was in the opera, and I thought the comedians must do better; and indeed, as far as I can judge they are much more correct; I was not therefore deterred from fixing on one who was guilty of no blunders which I was able to detect, who spoke very clearly and distinctly, and whose tones and actions were perfectly natural, though perhaps rather too faintly marked for stage effect; and I applied to him for some instruction in Italian. He seemed to be quite willing to assist me, but as this was just before the eight days of the carnival, he requested me to postpone the scheme for about ten days, as the company intended to stay the Lent in Rome, when he should have nothing else to do; however the company changed their mind, and went away immediately, and I lost my master. It was quite a disappointment to me, for he seemed very pleasing in his manners, and moreover was a Tuscan, so that I promised myself great advantage from the scheme. On missing him I procured another, with whom I am very well pleased, and of whom you have just heard my attendant’s criticism. One of his greatest faults is, that he is much given to flatter his pupils. Now the Carnival is over, Rome seems dead. The contrast is very striking, as the change takes place in a single day, and the gaiety does not diminish gradually, as at London, and the English watering places. The weather is delightful, and if the sun is rather too hot, it is easy at present to find shade; and while sitting to draw under the shelter of some venerable monument of antiquity, contemplating the clear blue sky, and some richly tinted ruin, while a mild and gentle breeze wafts perfumes from the beds of violets around, I seem to be as near an earthly paradise as imagination can conceive. I wish I could bring you here just for a moment, and show you what Rome is, and make you feel a Roman winter; yet I am told they are not always so fine, but that they usually have two months of continued wet. What astonishes me is to see the trees without leaves during all
- 54. this warm weather; the vegetation even now, is not much more forward than in a favourable season in England, but it is advancing with great rapidity. I must however turn away from all this trifling, to my more serious object of pursuit, and having given you an account of St. Peter’s, and a sketch of the principal ancient churches of this city, I shall now survey some of the modern ones. The most common arrangement of these is that of a nave with three arches on each side, opening into chapels; or in the more magnificent ones, with side aisles and chapels beyond them. In the centre is a dome resting on four piers. There is one arch in the length of each tribune, with the addition of a semicircular end to the choir: sometimes there are four arches, or five, instead of three, in the nave, and sometimes one or two smaller ones besides the three larger. The order is always Corinthian, and the nave a continued vault, springing, not from the top of the cornice, but from an Attic, or continued pedestal above it. The windows are generally groined into this vault, but sometimes the pedestal is cut to make room for them, and they are partly in the vault, and partly in the upright, which is displeasing. The principal arches opening into the nave, sometimes reach to the architrave of the principal order, and sometimes fall considerably short of it. In the latter case they have a gallery, or a panel, or perhaps something like a window over them, but the arrangement is much more beautiful when these arches are carried up to the full height of the opening, and the key-stone seems to contribute to the support of the entablature. This connects them with the principal order, with which otherwise, they have not sufficient union. When the parts are well proportioned, it is impossible to refuse our tribute of admiration to these churches; and if indeed it may be said with truth, that there is not one good front to any church in Rome, yet internally, they surpass, beyond all comparison, those of every other city. To produce the best effect, the pedestal above the cornice ought to be unbroken; and perhaps a wide plinth, without any mouldings, would be better than a pedestal. It is probable indeed, that the frieze and cornice of the principal
- 55. order might be omitted with advantage, but I am only going to theorize so far as to select the best parts of such as really exist, not to wander in the realms of imagination without a guide. The vault should be in coffers, and have the look of a stone vault; not pretend to be a peep into heaven, which is frequently the idea intended to be conveyed, and a heaven adorned in general with a very whimsical painted architecture, such as would not be at all commendable here on earth. The Italian artists have been very fond, in these paintings, of contradicting the architecture, and making their lines appear straight on a curved surface, and representing on the vault of a church a range of upright piers or columns; such a design is assuredly in bad taste, for the building would be much worse with such an addition; and in practice it has this further defect, that it can only look well from one point, and from every other is more or less distorted. The Jesuit Pozzi was famous for the skill with which he executed these deceptions, and I have already mentioned a production of his at Siena, which is admirable, as far as the mere accomplishing a thing apparently very difficult, can deserve admiration. The gilding (and say what you please about simplicity, the advantage of gilding is frequently very great) ought to be principally in the vault. The Attic should have little or none; it should appear again in the cornice, in the capitals of the pilasters, and in the key-stone of the arches. The impost of the arch should receive a little of it. Thus being gradually lost as it comes downward, it will produce the effect of richness without glare, and without separating the building into distinct and unconnected parts, a fault I have already noticed to you in St. Peter’s. In the disposition of the gilding two faults are always to be avoided, this separation into parts, and the too equal and regular distribution on all the similar members of the architecture. It is surprising how much gilding may be employed without any effect of richness, by this too regular and equal distribution; and I shall mention to you by and by some churches in Rome, where there is a considerable portion of gilding, but without any effect; a failure arising entirely from this cause.
- 56. In stating how a building of this sort should be managed, the greatest difficulty is in the manner of introducing the light. Three different methods offer themselves to our choice; the first is to light the nave by one large window at the end. There would then also be a large window at each end of the transept, and the choir would be comparatively dark; but the altar, if brought forward in front of it, and receiving the light from both transept windows, and from the dome, which would remain with lights round the drum, as at present, would occupy, as it ought to do, by far the most conspicuous and best illuminated point in the church. If the altar must be kept back towards the end of the choir, there should also be windows in the choir, not visible from the entrance of the building, in order to throw a strong light upon it, and give it its proper consequence. In either case I am persuaded the effect internally would be most beautiful, but I should be puzzled to make an equally beautiful outside. In a Greek cross, the whole might be lighted from the central dome, but this would not do in a Latin one. A second plan would be to keep the side aisles very lofty by omitting the frieze, cornice, and pedestal, of the order, and springing the vault immediately from the architrave, and lighting the edifice entirely from the aisles. A degree of solemn gloom would result from the comparative darkness of the upper part, which perhaps would not be inconsistent with a religious edifice. The third plan is to introduce semicircular windows over the order, and to groin them into the vault. The perfect continuity of the design is in some degree injured by this arrangement, yet it cannot be considered as objectionable, if care be taken that these windows do not interrupt the leading lines of the architecture. If the whole curve be divided into five panels, and these windows occupy only the lower, the light would be amply sufficient. Having thus endeavoured to give you some idea of the general distribution of the parts in the churches of Rome, I shall proceed to particularize a few of the finest examples, beginning with the Church of Sant Andrea della Valle, which I think on the whole deserves the first place. Here the nave has three arches on each side, besides a
- 57. smaller division towards the dome. This alteration of design is a defect. The piers of the dome ought to be decidedly distinguished from the rest, both by their larger size, and by some contraction of the width of the opening; but there is no reason to make the adjoining division smaller, or of a different character, for it will always connect itself to the eye with the nave, and not with the dome; and consequently communicate no character of strength and firmness. Perhaps the architect (Olivieri) considered these smaller openings, with the piers on each side of them, as forming each in fact, one great pier; but if such was his idea, he has entirely counteracted its effect by making openings in the mass. The order is bold and magnificent; the vault is nobly divided into three large panels, but unfortunately, as the ornaments have never been executed, the present appearance is rather bald and unfinished. This vaulting springs upon detached pedestals, which would be better if continued, and the windows occupy part of the space between them, and also part of the first division of the vault. The transepts have each two small divisions without side aisles, the choir has one small arch on each side, and beyond that a semicircle. The proportions altogether are very fine, and the effect truly sublime. Yet it is a sublime of a very different character from that of a Gothic cathedral, and I think seldom fully understood by the English. We expect from habitual associations, a different sort of impression, while the Italians, from similar causes, do not readily see or feel the merits of the Gothic. All however will admire the beauty of Domenichino’s exquisite frescos, which I will not describe to you, for I could not do them justice. There is a chapel in this church said to be built after designs left by M. A. Buonarotti, and whose ornaments are copies of some of his most celebrated works. It is oblong on the plan, and covered with a cupola, which this shape of the building renders slightly elliptical. This always appears defective; it seems too much like a circle badly drawn. Four columns on each of the three sides, make a sort of front to each, with a large semicircular window above one of them. The architecture is much broken, which though not to be admired
- 58. anywhere, is much more tolerable in tombs than in large edifices. Before the basement of these fronts are sarcophagi of a bad shape but of a rich material, being of the black and gold marble. The columns are of lumachelli; the beauty of the design consists in the harmony of all the parts, both as to form and colour (except some ridiculous new moons and flames on the pendentives). The Church of St. Ignatius, like so many other churches in Rome, and other parts of Italy, is the result of private magnificence, having been erected at the expense of Cardinal Ludovico Ludovisi, who left a sum of 200,000 crowns for its completion. Domenichino made two designs for this edifice, of which Father Grassi, a Jesuit, compounded the one which was executed. Domenichino was so much offended at this, that he refused to have any thing more to do with the building. How much the defects we now see in it are attributable to this procedure, it is impossible to decide. The circumstances which displease us are, that the side arches spring from little columns, and that whitewash is mixed with the rich marbles. The vault is smooth, and painted by Pozzi, with an ingenious perspective of bad architecture, and angels hanging about it. The cupola has not been executed. The general proportions are good, but the order is by no means equal to that of the Valle; still it is a noble church. I sometimes think that a considerably greater proportion of height to the breadth would be desirable in this arrangement, which additional height ought to be given almost exclusively to the order. This notion may have arisen from the habit of admiring Gothic churches. Yet in the narrow courts of their hypæthral temples, the Greeks seem to have been aware of the great effect produced by a height very considerable in proportion to the breadth. The Church of the Jesuits was built from a design of Vignola, and is worthy of his talents. Here the columns are doubled on the piers of the nave, and as in Sant Andrea there are three arches on each side, and then next to the dome, one smaller division without an arch. This interruption of the design disappoints the eye, and it is more objectionable here than in the former instance, because the piers of the centre are of themselves considerably larger than the
- 59. others, and it is therefore impossible to consider this division for a moment, as a large perforated pier. The side arches do not occupy the height of the order, but leave space for a gallery between them and the architrave. Above the order is a continued but broken pedestal on a high plinth, and a noble, richly ornamented rib; the whole width of the pier seems to form the solid of the vaulting. It is a pity that this fine feature should be interrupted to make room for the painting. The upper windows are badly ornamented, but they are rich, and in this part mere richness is of great value. Wherever the eye fixes, the architecture ought to be pure and correct, but the vaulting is seldom examined in detail, or at least the beauty of detail is there of less importance to the general impression produced by the building, than in parts more subject to inspection; and on the other hand, it is that part where richness of ornament produces the greatest effect in communicating to the building the appearance of magnificence. The chapels of the transept are very splendidly decorated, and on the whole, it is a most noble and magnificent church, and one of those which best satisfies the eye. It neither wants height, nor length, nor breadth; all is as it should be, and the defects are only in the distribution of the smaller parts. The width of the nave between the pilasters in this church, is about 55 feet, in Sant Ignazio, 57; in Sant Andrea, 51. Compare these with our St. Paul’s, which is 41, and you will easily understand that the Roman buildings, wider and shorter, and more richly decorated, must possess a character quite different from any thing to be seen in England. The Church of the Santi Apostoli is a fine edifice of this sort, with some of the chapels of rich and beautiful marbles well disposed, and in other respects highly decorated, and others of striped stucco; a contrast not at all pleasing. The parts in elevation, on the sides of the nave, are well proportioned, but the building does not end well, and is perhaps rather too short; the vaulting springs from a pedestal above the cornice. The lines of the architrave are interrupted to make room for an enormous picture, which represents not the fallen, but the falling angels; and in order to figure them in a more lively manner, the artist has made use of projecting portions of surface brought over the frame of the picture,
- 60. on which he has painted parts of the figures, as if they were then actually tumbling into the church. It is rather a misfortune, that so bad an idea should be so well executed. To carry you in detail through all the churches in Rome, would only offer a repetition of the same criticisms, without equal beauties to redeem their defects. Passing over therefore, a number of others of somewhat similar arrangement, and which all follow the disposition of the Latin cross, there are some very beautiful ones, in which that of the Greek cross is observed. The best of these, and the master-piece of Rainaldi, is the church of St. Agnes in the Piazza Navona; and a very delightful little building it is. The four equal arms are all very shallow, occupying four sides of an octagon, and it is an admirable lesson on the advantage of shallow recesses; although the little niches introduced at the extremities of the transept have a bad effect. Such a form might be very well lighted from the dome alone; but in the present instance this is too high, both for internal and external effect. The front is by Borromini, and though not free from his extravagancies, and his idly crooked lines, is the finest thing he has done. He had always some feeling among his wildest dreams, and it is this that at one time made him popular, and his example dangerous; had he not, he would neither have been admired nor imitated. Even in the church of San Carlo alle quattro fontane, where he seems to have given full reins to his imagination, we feel that there is something to be admired, though it is difficult to point out where it is; for on the inside as well as on the out, he has exerted himself to disappoint in every respect, both the eye and the judgment. His followers lost his beauties and preserved only his absurdities, thinking apparently, that the grace which still appeared, was owing to deformity, instead of, as was actually the case, feebly appearing through it. Bernini has built the Church of Sant Andrea del Noviziato, on the Quirinal, in an elliptical form, to which, I suppose, he was determined by the shape of the ground; and in interrupting the lines of the entablature for the great altar, and making that opening, and that of the doorway, greater than the rest, he was probably guided
- 61. by the prejudices of his employers. He has shown great judgment in avoiding anything of a transept, which must probably have given rise to another interruption, by making four chapels on each side, instead of an uneven number. The oval dome has something of a crooked appearance, and the details are not good, yet in spite of its defects, it is internally a beautiful little building. Of the outside, I will say nothing, for there is nothing good to be said. The front of the Church of Santa Maria di Consolazione, is perhaps among the most tolerable of those in Rome, where any considerable enrichment has been attempted; but there are three little churches or chapels in the same neighbourhood, where probably the builders were not rich enough to be absurd. The composition of each presents nearly a square face, ornamented with four Doric pilasters, and crowned with a pediment. The parts are differently disposed in each, but all have a pleasing simplicity of character. If I mention to you Santa Maria in Campitelli, it is rather because it is praised by others, than in compliance with my own taste. An effect of splendour is obtained by a multiplication of parts, without much dependence on each other. It puzzles rather than pleases.
- 62. W LETTER XXVIII. ROME. Rome, 7th April, 1817. e have had some rain here lately, and a good deal of snow upon the mountains; for the Apennine summits present a much greater mass of white than they did at the end of January. In the lower country the winter seems to be gone. The Anemones (Anemone hortensis) have been very plentiful and beautiful; they are now almost over, and the orchideæ are beginning to show their flowers. The weather is delightful, the sun, though bright, is not oppressive, and the night wind is no longer cold. The woods of Monte Mario are perfumed with rosemary in full flower; vegetation is everywhere vigorous and beautiful, and all nature feels the genial influence of the season. A first of April at Rome is all you can imagine of a May day in England. But enough of nature; I am about to give an account of art; of pomps, and processions, and ceremonies, where all is artificial. They began the 30th of March, which was Palm Sunday, and I went to the Sistine chapel to see the palm branches distributed. These palm branches look like reeds with the leaves still upon them, all of which, except two or three at the top, are plaited up, so that they are not very unlike slender rods covered with yellow ribbon; they are said however, to be real palm tree leaves. One of these is given to each of the cardinals, together with a branch of olive. When arrived at the Vatican, the doors of the great hall (the Sala regia) were shut, and a considerable number of people were waiting at the head of the stairs. We understood that no general
- 63. admission would be given till the procession had passed, i. e. the pope and cardinals had entered the chapel. After a little time, the doors were thrown open and we entered the hall, but a circuit of soldiers placed about the door prohibited our immediate entrance into the Sistine Chapel. One by one we slipt through, the intention apparently not being to prevent us entirely from entering, but merely, by retarding our motions, to avoid bustle and confusion. It was however some time before I could work myself up into a good position, and that moment the pope, and all the cardinals were seated. The latter held in their hands the palm branches, and at the feet of each an attendant was seated who held an olive branch. A priest at the altar was saying mass, but the pope seemed quite the object of attention, and almost of adoration. We might almost at times fancy the music repeating, “We worship thee O Lord, the Pope,” so well did the action correspond with such an expression. The ceremonies were not much varied; they consisted principally in alternately getting up and sitting down, while at each change of position the attendants arranged the robes of their superiors. Two of these waited on the pope, and disposed the folds of his garments very carefully every time he moved. Sometimes the cardinals advanced from their seats, and passing through the row of attendants, knelt down to the pope and the altar, laying their palm branches on the ground. During part of the service, the pope wore a mitre, which was put on, and taken off, with great ceremony. On one occasion he rose from his seat, and walked to a cushion placed in front of the high altar, upon a sort of stool. On this he knelt down, and his attendants took off the mitre. The music suddenly ceased, and there was a dead silence, all the cardinals and attendants being at the same time on their knees. The effect of this silent prayer is very impressive. It was a pity the spectators could not kneel too, but it was impossible for want of room. The two attendants of his holiness meanwhile spread his robes carefully over the elbows of the cushion, and disposed his train symmetrically, turning out on each side a quantity of the white satin lining; a sort of parade very injurious to the solemnity of the scene, as it drew down the attention from every sublime sentiment, to a trifling, and even
- 64. contemptible object. The service in general did not appear very impressive, and there was hardly any music except a monotonous recitative. On Monday and Tuesday nothing was done. On Wednesday afternoon there was again service in the Sistine chapel. It began about five o’clock, by candle light, for even at noon day candles are used; amongst these was a row of fifteen lights, intended to represent the twelve apostles, and the three Mary’s, and these were extinguished or expired at irregular intervals, to show that they did not all abandon our Saviour at once. After fourteen of these were out, the remaining one, which we were told was to represent the Virgin Mary, was taken down, and all the other lights in the room extinguished, leaving only the faint remains of day (it was then near seven o’clock) and in this state we heard a fine piece of music, the effect of which was perhaps enhanced by the gloom. On Thursday morning I was at the Vatican about nine o’clock, but was refused admittance because I wore trowsers; I therefore returned to change my dress, among a great number of my countrymen, who were in the same predicament; but I returned before mass had begun in the Sistine chapel. I did not however attempt to enter, as it would only have been a repetition of what I had seen before. The Paoline chapel was very splendidly illuminated, and after a short time the consecrated wafer was carried in procession, and laid in what is called a sepulchre in that chapel, where a painted body is exposed, intended to represent that of Christ. As this room is much smaller than the Sistine chapel, I thought I should have no chance of obtaining admittance, and repaired to the hall where the feet of the thirteen pilgrims were to be washed by the pope. It is a large room, and on the left hand side of it, was a seat a little elevated, on which these men were seated, each dressed in a cloak of white cloth, lined with silk of the same colour, and trowsers also of white cloth. On the right were three or four ranges of seats for the ladies; in the middle stood the gentlemen, of whom a large number were already collected. A part at the upper end, was railed
- 65. off for his holiness and the cardinals, with a station for foreign ambassadors; and there were four boxes, into the first of which the old king of Spain shortly entered. The queen of Etruria took possession of another, accompanied by her son, who has the reputation of being a very amiable and accomplished gentleman; the third received the duke del Genovese, and the duchess of Chablais; in the fourth was the prince of Prussia. All these people had been at the Sistine chapel in boxes prepared for them in like manner, but I forgot to mention the circumstance. After the entrance of the pope a short service was chanted. Two cardinals then replaced the mitre on the pope’s head, and took off his robes; two attendants held up his petticoats in front, that he might be able to walk down from his throne, and two cardinals held up his train behind. The upper garments which he had just laid aside were crimson, embroidered with gold, the under ones, which he still wore, were white. Thus accompanied, he descended to the place where the pilgrims were sitting, each of whom bared his right foot, on which in succession, the pope poured a little water, and taking the foot in his hand wiped it with a napkin. What would you think in London, if the Prince regent and lord Castlereagh were to get up a political comedy, and act themselves the principal characters, and each sing his song? Here religion forms the politics of the place, and the subject is quite a religious comedy, or as Hannah More might call it, a sacred drama. But custom sanctions these usages, and that is now venerable, which if it were to originate in the present day, would be merely ridiculous. I was here one of a party of four Englishmen, all about as tall as myself, but we were overtopped by the whole head by another of our countrymen in the room. I missed the supper, which perhaps you will think no loss; and after passing some time in St. Peter’s, and the galleries of the Vatican, places which never lose their interest, I retreated to my usual trattoria, but returned in the evening to hear the Misereri, at St. Peter’s. It was sung beautifully, but the voices seemed hardly strong enough to fill even the side chapel where it is performed. It may help to give you some idea of the size of St. Peter’s, to tell you that several services are sometimes performed at the same time without in the least interfering with