Transcriber’s Notes: The spelling, punctuation and hyphenation are as the original, with the exception of apparent typographical errors which have been corrected. Italic text is denoted _thus_. Bold text is denoted =thus=. [Illustration: THE MAIN POST-OFFICE, PHILADELPHIA.] THE PNEUMATIC DESPATCH TUBE SYSTEM OF THE BATCHELLER PNEUMATIC TUBE CO. ALSO FACTS AND GENERAL INFORMATION RELATING TO PNEUMATIC DESPATCH TUBES BY B. C. BATCHELLER, B.Sc. MECHANICAL ENGINEER [Illustration] PHILADELPHIA PRESS OF J. B. LIPPINCOTT COMPANY 1897 COPYRIGHT, 1896, BY B. C. BATCHELLER. CONTENTS. CHAPTER I. A BRIEF HISTORICAL SKETCH. PAGE EARLY RECORDS 9 PRACTICAL BEGINNING OF THE ART—THE LONDON PNEUMATIC TELEGRAPH 10 THE SIEMENS CIRCUIT SYSTEM 14 RECENT IMPROVEMENTS IN THE LONDON SYSTEM 16 AN UNDERGROUND PNEUMATIC RAILWAY FOR TRANSPORTATION OF MAIL 19 THE BERLIN PNEUMATIC TELEGRAPH 20 THE PARIS PNEUMATIC TELEGRAPH 22 THE PNEUMATIC TELEGRAPH OF OTHER CITIES 25 PNEUMATIC TUBES IN AMERICA 25 CHAPTER II. THE PNEUMATIC TRANSIT COMPANY AND THE FIRST PNEUMATIC TUBES FOR THE TRANSPORTATION OF UNITED STATES MAIL. ORGANIZATION 28 AIM AND OBJECT OF THE COMPANY 28 THE CLAY-LIEB PATENTS 30 FRANCHISES AND FIRST GOVERNMENT CONTRACT 33 SEARCH FOR TUBES 34 METHOD OF MANUFACTURING TUBES 35 LAYING AND OPENING THE TUBES FOR TRAFFIC 37 DESCRIPTION OF THE TUBES, METHOD OF LAYING, ETC. 38 THE AIR-COMPRESSOR—METHOD OF CIRCULATING THE AIR 40 TERMINAL APPARATUS 42 THE SENDER 43 SUB-POST-OFFICE RECEIVER 44 MAIN POST-OFFICE RECEIVER 47 THE CARRIER 50 OPERATION OF THE TUBES 52 BENEFITS OF THE SYSTEM 54 CHAPTER III. THE SYSTEM AND APPARATUS OF THE BATCHELLER PNEUMATIC TUBE COMPANY. GENERAL ARRANGEMENT AND ADAPTABILITY OF THE SYSTEM 57 THE SIZE OF TUBES 64 SYSTEM OF VERY LARGE TUBES 65 GENERAL ARRANGEMENT OF APPARATUS IN THE STATIONS—TWO-STATION, TWO-COMPRESSOR LINE 69 TWO-STATION, ONE-COMPRESSOR LINE 72 THREE- TO EIGHT-STATION LINE 74 SENDING APPARATUS 79 SENDING TIME-LOCK 84 INTERMEDIATE STATION TIME-LOCK 88 ELECTRO-PNEUMATIC CIRCUIT-CLOSER 91 THE OPEN RECEIVER 94 THE CLOSED RECEIVER 99 THE INTERMEDIATE STATION RECEIVING AND TRANSFER APPARATUS 106 CARRIERS 115 AIR SUPPLY 117 FANS 117 BLOWERS 117 AIR COMPRESSORS 118 THE TUBE, LINE CONSTRUCTION, ETC. 122 CHAPTER IV. FACTS AND GENERAL INFORMATION RELATING TO PNEUMATIC TUBES. DEFINITIONS 124 INTERMITTENT AND CONSTANT AIR-CURRENT 125 LAWS GOVERNING THE FLOW OF AIR IN LONG TUBES 126 LAW OF PRESSURE 128 USES OF PRESSURE CURVES 130 LAW OF VELOCITY 130 CHARACTERISTICS OF THE VELOCITY CURVE 132 USES OF VELOCITY CURVES 133 QUANTITY OF AIR USED 134 TEMPERATURE OF THE AIR 135 HORSE-POWER 136 EFFICIENCY 137 PRESSURE AND EXHAUST SYSTEMS 138 LAWS EXPRESSED IN MATHEMATICAL FORMULÆ 141 MOISTURE IN THE TUBES 142 LOCATION OF OBSTRUCTIONS IN TUBES 143 PREFACE.