648 TRANSACTIONS OF THE AMERICAN INSTITUTE, 



travel over much steeper grades than any now found, even on 

 railroads worked by horses. There appears to be in the theory 

 of re-charging while in motion no difficulty which cannot be over- 

 come by a proper arrangement of the details, and, in addition, if 

 necessary, by reducing the speed on approaching a supplying 

 station, and increasing it again after passing. In regard to the 

 commercial advantages or disadvantages of the system as com- 

 pared with those now in use, there are many points which can 

 only be determined by experience ; but the following may, how- 

 ever, be considered as definitely established : 



" 1. That making due allowance for the great economy of 

 engines employed in pumping, over all varieties of engines for 

 ordinary purposes, the cost for power at the pumping stations 

 will be only about one-quarter as much as that now developed in 

 steam locomotives, reckoned horse for horse. 



" 2. That coal may be used for fuel at the best advantage — a 

 point which, though much striven for, has not yet been attained 

 in locomotives (April, 1858). 



" 3. That tight, safe, and in every respect efficient receivers 

 can be constructed sufficiently light to be placed in the cars, and 

 in this respect to allow this system to be worked with advantages 

 over either the steam locomotive or the horse systems, on a very 

 great majority of lines, 



•' 4. That the track will endure longer in transacting a given 

 amount of business by this system, than under the crushing 

 weights of locomotive steam engines. And 



" 5. That grades steeper than are ever worked with steam 

 locomotives could be allowed on a road worked by this system, 



'•Your system allows of working by long trains of cars, cou- 

 pled together in the ordinary manner • but is peculiarly adapted 

 to the running of cars, singly, or in very small trains, and at 

 short intervals, for the better accommodation of the traveling 

 public. The air might be worked expansively with advantage 

 by the ordinary link motion, and the engine be made capable of 

 reversing. But simplicity is a matter of great importance, and 

 I have constructed tables presented herewith, in such manner 

 as to show the results due to the working by the simplest pos- 

 sible mechanism without expansion. The points presented in 

 these tables are capable of being exactly ascertained by mathe- 

 matics alone. But the effect can be very materially increased 

 by working it expansively. By cutting off at one-fourth of the 



