Report of the Committee on Steam Boilers. 77 



tube variety. There are ninety -four (94) tubes, C, each two (2) inches 

 in diameter, and four and a half (4£) feet long. In the smoke-pipe is 

 placed an arrangement, S, for superheating the steam, composed of two 

 hundred and sixty-nine (269) one and a quarter (1£) inch tubes, each 

 one and a half (1£) feet long, and above this is a feed water heater, F, 

 consisting of the same number of one and a quarter (1£) inch tubes, 

 each two (2) feet long. In the competitive test of this boiler, the feed 

 water heater was used, but the steam was not passed through the 

 superheater, but was drawn directly from the steam drum, D. This 

 drum is twenty-two (22) inches in diameter, and thirty (30) inches 

 high. 



Calculations. 



All calculations are given in detail, in exhibits F, G-, H, I, and J. 



In calculating the results from the record of the logs, the committee 

 first determined the amount of heat carried away by the condensing 

 water, by deducting the temperature at which it entered from that 

 at which it passed off. 



To this quantity is added the heat which was carried away by 

 evaporation from the surface of the tank as determined by placing a 

 cup of water in the tank at the top of the condenser, at such height 

 that the level of the water inside and outside the cup were the same, 

 noting the difference of temperatures of the water in the cup and at 

 the overflow, and the loss by evaporation from the cup. The amount 

 of evaporation from the surface of the water in the cup and in the 

 condenser, which latter was exposed to the air, was considered as 

 approximately proportional to the tension of vapor due their tem- 

 peratures, and was so taken in the estimate. The excess of heat in 

 the water of condensation over that in the feed water, also evidently 

 came from the fuel, and this quantity was also added to those already 

 mentioned. 



The total quantities were, in thermal units, as follows: 



Root 34,072,058.09 



Allen 48,241,833.60 



Phleger 24,004,601.14 



Lowe 38,737,217.57 



Blanchard 11,951,002.10 



These quantities being divided by the weight of combustible used 

 in each boiler during the test, will give a measure of their relative 

 economical efficiency ; and divided by the number of square feet of 

 heating surface, will indicate their relative capacity for making steam. 

 But as it is the intention of the committee to endeavor to establish a 



