PHILOSOPHICAL SOCIETY OF WASHINGTON. 31 



It was found that it required more power to push the same loco- 

 motive on curves when the wheel base was so arranged that the 

 front end of the locomotive was free to swing in a cradle of the 

 truck (as at certain velocities, the centrifugal force would act upon 

 the locomotive in such a manner that the flanges of the driving 

 wheels against the rails would guide the engine; the front out- 

 side driving-wheel flange would be against the outer rail, and the 

 rear inside driving-wheel flange against the inner rail), than it 

 did when the same locomotive was so arranged that the front 

 truck and the rear driving-wheel flange guided the engine. This 

 is seen practically in its eflPect upon the wear of rails on different 

 roads; the outer rail of curves on the B. &ORR PW& 

 B. R. R., N. Y. & H. R. R., N Y. C. & H. R. R. R. being 

 but very little more worn than upon the tangents while upon the 

 P. R. R. the wear of outer rails on curves has been much more 

 rapid. 



Generally speaking, it has been found to require less coal to run 

 freight trains at an average speed of 18 to 20 miles an hour, than 

 from 10 to 12 miles. But few time tables are arranged in accord- 

 ance with the gradients of the road. On some roads uniform 

 speed is required over all portions of the road, which practically 

 lessens the number of cars drawn per train ; while if the time 

 tables wer.e arranged in accordance with the work, from two to 

 three more cars could be taken on the ordinary trains. The con- 

 struction of cars for the same purpose is so different in detail, 

 that their resistance to traction varies ; so that it seems impos- 

 sible to determine anything more than an approximate formula 

 for general application. Changes are made upon mere opinion, 

 without a knowledge of facts. In locomotives where perhaps 

 more pains are taken to systematize matters, we find in those said 

 to be made from the same drawings, a variation from ten to twenty 

 per cent, in their capacity. This is a common observation of 

 engineers and master mechanics, derived from their daily expe- 

 rience. Some engines will give a very smooth diagram, while 

 others will show great irregularities (on the same track), due to • 

 steam admission or counter balance. Each engineer gives a per- 

 sonal equation to the diagram. The rate of adhesion varies also 

 for the same weight in different engines, and is much greater at 

 slovv speeds than at high ones with the same engine. 



In drawing freight trains the greatest range of variation in 

 resistance is due to the wind ; stock cars giving the highest rate. 

 Loaded box cars in trains of twenty to twenty-five cars give on a 

 level and straight track from four to six lbs. resistance per ton; 

 while thirty empty stock cars gave 13.20 lbs. per ton on a windy 

 day. Trains are now limited in length, from the uncertainties 

 of changes of weather during their transit. As soon as the mat- 

 ter is more thoroughly understood by the railroad people, I hope 

 to see trains dispatched in accordance to the Signal Service indi- 



