10 TRANSACTIONS OF THE [nOV. 3, 



indicates the proper intervals, each one being a complete revo- 

 lution of the circuit-breaker, so that each interval is ab.^oliitelj 

 the same in time, which is not the case with a circuit-breaker of 

 a wheel composed of many teeth. 



The lines which show the consumption of each cul)ic foot of 

 water, each 25 or 50 lbs. of fuel, velocity of wind, revolutions 

 of drivers, intervals of firing, and duration of black smoke are 

 not here shown, as the indications are made through some of the 

 electric recording pens, which are similar to those giving elec- 

 trical records regardino- the track on Fis;. III. 



Any special piece of electrical recording apparatus can be put 

 in circuit with a pen, and its indications recorded. The dyna- 

 mometrical curve shown on Fig. III. was from a heavy freight 

 train, moving at about 14 miles per hour on a line of short 

 curves. The fluctuations of the line for each revolution of the 

 drivers is very slight here ; sometimes it varies 1000 to 2000 

 lbs. per revolution, when a large freight locomotive is working 

 nearly to its maximum power. 



On the right may be seen the effect of poor joints and rails. 

 A short diagram, representing but a portion of a line, gives 

 but little idea of the fluctuations of a dynamometrical curve 

 of a train drawn over a division of a railroad. A tabulati(jn of 

 the data per mile gives but little in regard to the details of the 

 fluctuations due to topographical features of the line, or local 

 conditions regardino- the track. 



In starting a train the locomotive usually works for a few feet 

 up to its full tractive power, from 12,000 to 20,000 lbs., accord- 

 ing to capacity and size of train, then the line falls as the speed 

 increases, quite rapidly at first and then slower until the curve 

 reaches a comparatively uniform height for the tractive powei- 

 exerted by the locomotive, generally about one-fourtli of the 

 amount used in starting. All movements of the cut-off, up or 

 down, or of the throttle valve, in or out, are shown by the 

 curve. Aside from all other conditions, each engineer, espec- 

 ially on a freight train, giv^es the curve a personal equation, a good 

 one, if he is a first-class runner, thoroughly acquainted witli the 

 line, so he is alfle to work his locomoti\'e to the best advantage, 

 saving in fuel and time. Such engineers can draw more cars, 

 with a given locomotive, than those who are not so well versed. 



The original diagrams, representing the dynamometrical 

 curve together with the chronograph line, set forth what is 



