CHAPTER IV

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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.

I have been prompted to prepare this book by the frequent inquiries made regarding the details of our system of pneumatic tubes. These inquiries have come from people interested in our company, from others interested in companies that have purchased the right to use our apparatus, from people desirous of becoming interested in a pneumatic-tube business, from would-be purchasers of pneumatic tubes, and from people interested in pneumatic tubes from a scientific, engineering, or mechanical point of view. This book is not intended to be a treatise on pneumatic tubes. In the first