RAIL-UOADS. 553 



The Rocket performed seventy miles in six hours and two 

 minutes, or over eleven and a half miles per hour, includ- 

 ing stoppage. The distance from Liverpool to Manches- 

 ter, thirtytwo miles, has been travelled over with passen- 

 gers, in a little more than two hours. 



The following among many data on this subject, havo 

 been ascertained from the laws of Natural Philosophy and 

 from extensive courses of experiments. 



1. That air as a resisting medium, (unless irregular in 

 the shape of wind,) makes no perceptible difference at 

 increased velocities on a rail nay. 



2. That on a well constructed railway, the friction or 

 resistance is that of the axle or a rubbing friction, and 

 the slight adhesion of rolling upon the rail. 



3. That the friction on a level is nearly as the weight, 

 and the tractive force required, therefore, nearly the same 

 at different velocities. From this we see that if weight 

 is reasonably reduced, there is scarcely a limit to the lo- 

 comotive power of steam, so long as the pistons can 

 work and the wheels can turn. 



4. That a horse exerts his greatest available power at 

 two to two and a half miles the hour, and beyond this 

 rate the horse requires the greater portion of his muscu- 

 lar action to propel hitntclf forward, leaving but little for 

 the load. At his customary rate seven eighths of his 

 force is exerted upon himself, leaving one eighth only for 

 the load. As the velocity increases, the proportion re- 

 maining for the load is of course diminished. In Eng- 

 land every coach on the best roads that runs for twenty- 

 four hours at nine miles per hour, drawing not over two 

 tons, requires no less than 180 horses or ninety each way. 

 Less than twelve horses would carry the same weight for 

 the same time on the same roads at two and a half miles 

 per hour. 



A horse can, at a dead pull, walk pff raising 5 to 600 

 pounds over a pulley, but the average of his tractive pow- 

 er when in regular employment, is not above seventyfive 

 pounds. 



The experiments of Leslie and others on this subject, 

 give the following practical results applicable to rail-roads. 



