74 Traxsactioxs of the American Institute. 



by means of a letter Imng in the engine room with tlie regulations, 

 in which was the following, viz. : 



The cost of the power will be ascertained by measuring the feed 

 water with a meter open to the inspection of all. (Exhibit E). The 

 exhibitors gave their assent to this provision, and no protest was 

 made during the experiments. 



Not\vithstanding the above facts, it became necessary to weigh the 

 coal during the trials — 7iot for the judges of engines — but simply to 

 get at the evaporation of the boilers, as it was feared there would 

 not be time to test the boilers after the completion of the engine 

 tests. The coal account does not therefore properly belong in this 

 report, still I do not feel at liberty to suppress any of the facts that 

 took place at the time. The results showed that there was consider- 

 able more coal burned the first day than the second to evaporate sub- 

 stantially the same quantity of water. This may be explained in 

 various ways. The necessary position of the fires and fuel made 

 them at least liable to interested interference. It is not known that 

 this fact was taken advantage of. K not, the result proves the difii- 

 culty of ascertaining the coal accurately in short experiments, and 

 may be explained also from the fact that the boilers would easily 

 make much more steam than was required, so the first day the atten- 

 tion of the firemen was very constantly occupied in regulating the 

 steam pressure, and they were subject to less supervision also than 

 afterward when all interested had become accustomed to observing 

 the instruments in the main building. The result is useful as show- 

 ing how great a difference can be made in the performance of a boiler 

 by the simple management of the fires. The evaporation per pound 

 of coal the first day was 6.4 pounds of water, an inferior result. The 

 next day it rose to 8.2 pounds a very good result for any boiler 

 using cold water. The third day the result was Y.7 pounds. 



Attention is called also to the . fact, that if the coal were not 

 excluded by the conditions of the trial the results, it sh'oAvs, stand 

 unconfirmed by any other evidence and the quantity consumed, must 

 for so short a trial be considered a kind of guess work. The meter, 

 on the contrary, though varying its rate five times as mucli as one I 

 saw tested for the Croton department, was at least, positively accu- 

 rate, at the equal rates of speed during the experiments, as has been 

 shown, besides which it has the confirmatory evidence of the indica- 

 tor diagrams : for the engine which used a trifle more water by the 

 meter had a lower terminal j^ressure in the cylinder, and by the usual 



