180 Book of Engineering 



The mailmen know where they are exactly 

 by the sounds made by the train. Each 

 bridge passed over has its own particular 

 sound, each cutting through which the 

 train is rushing has a note all of its own. 



As an exchange point is reached the men 

 within the mail van put whatever bags are 

 due to go into one or more stout leather 

 pouches. As many as four light mail bags 

 can go in a single pouch. The pouch is 

 strapped ready, and is then clipped upon 

 the standard. When the sound of the rail- 

 way tells the man in charge that the train 

 is rapidly approaching the exchange point, 

 he pushes out the standard with its two or 

 three pouches, and at the same time drops 

 a net from the side of the van. Then an 

 electric bell begins to ring; it says " As you 

 value your life, do not pass this spot! ' 



No wonder, for there is the usual click and 

 the thud, and something black comes flying 

 into the mail van through the open door. 



It is the pouch picked up from the track- 

 side standard. Mails have been exchanged 

 at sixty miles an hour! 



