Jrach 



Distant 



gnalj 





I' 



fKTrain 



Showing a train seeking 

 to enter the block be- 

 yond the "home" sig- 

 nal. Engineer knows 

 by the fact that "dis- 

 tant" signal is up that 

 the home signal is also 

 up, even though he may 

 not be able to see the 

 latter, due to smoke, 

 fog, or an obstruction 



*K 



Engineer sees that the 

 distant signal is down 

 and knows that ' the 

 home signal is also clear. 

 He therefore goes ahead 

 at the regular or full 

 speed. A "home" sig- 

 nal is so called because 

 it is nearest "home '; 

 or in the block the 

 train .seeks to enter 



f 



Something is wrong. 

 The distant signal is 

 down without the home 

 signal being correspond- 

 ingly clear. This shows 

 how a block system 

 sometimes fails. Auto- 

 matic train control is 

 designed to stop the 

 engineer safely at home 

 signal in such a case 



Popular Science MontUy 



these much-needed contrivances, the Govern- 

 ment has for several years maintained a corps of 

 trained investigators who will go to almost any 

 part of the country and test out free of charge 

 any invention of the kind that gives promise of 

 being worth while. Moreover they will make an 

 authoritative report on its merits, if it proves 

 worthy of attention. This corps has given much 

 practical aid to inventors, and done much 

 through suggestions to standardize and improve 

 the inventions being put out. At present we are 

 on the road to a practical train-stop. 



To illustrate the general train-stop situation 

 specifically, we will show how one of the best 

 train-stops operates. Let us take the type 

 recently perfected by Jean F. Webb, Jr., of New 

 York city. As the pictures on page 438 show, 

 the apparatus is affixed to the buffer-beam at 

 the front of the engine. Other inventors attach 

 their stop to the tender, or even beneath the cab. 

 Some have attempted to locate most of the 

 apparatus along the roadway and have it struck 

 by a projection on the engine as the latter goes 

 by. This, however, seems to be a wrong plan in 

 most cases, since the great force of such a broad- 

 side impact may result in breaking the appa- 

 ratus to pieces. 



The ramp principle Mr. Webb uses is begin- 

 ning to be recognized as the most satisfactory out 

 of the number of alternatives. As the engine and 

 train approach a block signal, the shoe part of the 

 apparatus runs up a short piece of inclined 

 rail, or T-iron, say thirty feet long. This piece 

 of inclined rail is called a "ramp.' ' As the shoe 

 rides up over the ramp it opens the air valve on 



437 



The complication of 

 signals an engineer 

 encounters in an 

 ordinary railroad 

 yard which covers 

 an area about two 

 miles long and 

 about one and «ne- 

 quarter mile wide. 

 All tracks are single 

 tracks; the parallel 

 nes represent ra'. r 



r 



Showing more compli- 

 cated signals than the 

 preceding. Engineer 

 has whistled for side- 

 track. Towerman ac- 

 cordingly gave it to 

 him, at the same time 

 lowering the lower of 

 the two arms at the 

 home signal — which in- 

 dicates that everything 

 is ready for the train to 

 proceed to side track 



Still more complicated 

 signals, showing what 

 mixed up propositions 

 an engineer encounters. 

 He must read the sig- 

 nals almost instantly 

 and correctly or cause 

 trouble for himself and 

 train. Here signals 

 mean main line is closed 

 but sidetrack is open 



