Report of Supeeixtexdejkt. 69 



Cost of the Powek. 



Ba brock and 

 Wilcox 



s. "Water, per indicated horse power, 



per hour, pounds 25 .482 



t. Water, per net horse poM'er, per 



hour, pounds 29 . 231 



u. Water, per dynamometer horse 



]:)Ower, per houi-, pounds 31.007 



v=9. Coal, per indicated horse powei-, per 



hour, calcuhited from water, lbs. 2.831 



w=l. Coal, per jiet horse power, per hour, 



calculated from water, lbs 3.248 



ic=1. Coal, per dynamometer, horse 



power, calculated from water, lbs. 3.445 



Table ISTo. 2 is a brief summary of the results of the experiments 

 above described. The lines have been designated by letters for con- 

 venience of reference. 



The mean power developed in the cylinder during each trial, 

 in excess of that required to displace the back pressure of the 

 atmosphere, is shown in line "/!," marked "Indicated Horse 

 Power." 



The useful work done by each of the engines equals the power 

 traiismitted through its belt to the shafting, and must be obtained by 

 adding to the dynamometer horse power, the power required to over- 

 come the friction of the connecting shaft, which carried the receiving 

 pulleys of all the engines. The friction of this shaft M^as not the 

 game for the two engines. The belts of the engines were furnished 

 by different exhibitors of belts, and tightened according to their 

 differing ideas, which, under the eii'cumstances of a general exhibi- 

 tion, could not be properly interfered with by either of the engine 

 exhiljitors or myself. Foi; these reasons the belt of the Babcock and 

 Wilcox engine was very tight, and that of the Harris engine, which 

 was secured at the laps by cement only, w^as very loose, so much so, 

 that it slipped a little when the load was being regulated for com- 

 mencing the trial. In addition to this, also by the accident of posi- 

 tion, the driving belt of tlie second line of shafting pulled almosfc 

 directly opposite that of the Harris engine, and reduced materially 

 the friction due to the tension of both belts. No such action took 

 place when the Babcock and Wilcox engine was tried. " 



To ascertain the friction of the shaft under these varying condi- 

 tions, each engine was in turn ii.idicat<jd when driving the connecting 



