101 G Traksactioxs of the Americax Institute. 



rentine^ power, a man took more than he paid for, it was easy to see 

 what a loss followed. The average engines would use four and a half 

 pounds of coal per hour, and it was of great importance that every 

 man should know how much power was used, for if more was taken, 

 more coal must go into the furnaces. The rules for calculating the 

 power of steam engines are incorrect, as many mistakes are made by 

 the old method of calculation. The exact pressure can only be 

 determined by the indicatol' ; rules cannot be given. The boiler 

 pressure cannot always be tlie standard of calculation, for there is a 

 great difference in the pressure in tlie boiler and that in the cylinder. 

 Therefore, we must take, as the basis of our calculation, the pressure 

 in the cylinder while the piston is moving, and this is shown by the 

 indicator. Then we get the actual amount of the power of the 

 engine. lie spoke of this because there was a general misunderstand- 

 ing on this matter of measuring the power of the steam engine. 

 Duncan, in England, introduced the heat of the condensing water as 

 an element in the calculating of engine performance, and proves 

 those engines leaving the water at the lowest temperature to be tlie 

 most economical, since there was the least heat wasted. The expan- 

 sion of steam in the cylinder with the cut-off will reduce the tempera- 

 ture. 



Mr. James Montgomery stated, that since the first steamship, " The 

 Savannah," built in JSTew York, crossed the Atlantic in 1819, we 

 have been working by the rule-of-thumb. There is a great deal of 

 ignorance as to who builds the best engines. What we want to 

 know is how much steam is used, and how much power developed. 

 Also, what engine wastes the most power in friction. In renting 

 power, sometimes an inch of belt is reckoned a horse-power, and yet 

 he knew a man who with an inch and a half of belt managed to get 

 some fifteen horse power, and paying for only one and a half. If the 

 dynamometer is used in connection M'ith the indicator, a complete 

 revolution will be made in testing the power and economy of the 

 steam engine. The want of a thorough test like this is much felt in 

 our merchant marine. The indicator only tells us how much steam 

 each engine uses, but the dynamometer shows just how much power 

 the steam produces, and so indicates wlio builds the best engines. 



Mr. Sutton stated that the indicator placed on the engine at the 

 Mechanics' fair in San Francisco, gave some veiy strange diagrams. 

 He was asked what was the matter, but could not tell at first, but if 

 they would put his dynamometer on he could tell them wliat the 



