APPLIED MECHANICS LECORNU. 277 



maneuvering becomes simpler because of the reduced number of 

 couplings. 



Henry, who stated these facts in 1911 before the Societe d'Encour- 

 agement, is of the opinion that we may expect further development 

 and use of these cars of great capacity. However, the small cars will 

 always preserve thch utility for lighter trafiic, the great cars being 

 reserved for the heavier. 



The employment of the air brake has become general with passen- 

 ger trains, althougli in Europe it has not yet been extended to freight 

 trains. Such an extension is, however, very desirable even for the 

 security of the passenger trains, since the number of collisions between 

 freight and passenger trains occurs because the former have not 

 sufficiently powerful means of stopping. The air braking ol freight 

 trains \vill cost very considerably, but, as I stated in 1909, it is more a 

 technical difficulty which retards theh' use. Experience shows that 

 with the very long freight trains the change of pressure produced by 

 the engineer at the front end of the compressed air system requires a 

 considerable lapse of time before it is felt at the other end, and during 

 that period the couplings, which are generally made rather loose in 

 freight trains, because of the frequent changes recpiired in their 

 make-up, receive violent shocks, frequently breaking them. Sabou- 

 ret, the chief engineer of the Compagnie d'Orleans, proposed for the 

 overcommg of this difficulty a very simple and ingenious contrivance: 

 At the moment when the engineer manipulates the valve of the air 

 brake the three follomng effects are prockiced: First, the tender and 

 the four ffi'st cars are immediately braked; second, the engine is 

 braked progressively; and third, the rest of the train is braked -with 

 a retard of 10 seconds, sufficing for the cars, because of their acquired 

 velocity, to compress all the couplings by pushing forward. Experi- 

 ments have shown that, under sucli conditions, the braking works 

 satisfactorily. The application of the process in the Compagnie 

 d'Orleans would cost 7 to 8 millions of francs. 



While waiting for the provision of aii* brakes to freight trains, it 

 is indispensable to at least employ sure and powerful hand brakes. 

 For this purpose the Mestre brake should be mentioned. It last year 

 received the gold medal of the Societe d'Encouragement. In the 

 Alestre brake, by a very simple starter, a strong spring causes the 

 rapid aj)proach of the brake shoes, the final clamping being obtained 

 by a device analogous to that of a hand jack. This brake has been 

 successfully tried m the eastern section of France. 



The ruptures of the couplings to w^hich I have made allusion are 

 one of the plagues of the railroad world. The i)rocedure which 

 naturally occurs iu'st for reducing them is to reenforce aU the dimen- 

 sions, and such in a measure has been done, as the increase of loads 

 85360°— SM 1912 10 



