Eepobt of Superintendent. 71 



Tlie specific volumes of the steam were ascertained from tables 

 founded on the experiments of Regnault and others. 



The facts required for this calculation are shown in "table No. 1," 

 viz. : 1st. The terminal pressures from the indicator diagrams ; 

 2d. The atmospheric pressure shown by the barometer (the total 

 pressure equals the sum of the two), and 8d. The dimensions neces- 

 sary to calculate the capacity of the cylinder, clearances, &c., at the 

 termination of the stroke of the piston. 



Line )\ shows the per centage of the water used, which is accounted 

 for by the amount of steam present in the cylinder at the end of the 

 stroke. The deficiency in each case shows of course of the amount of 

 icater present with the steam at that point. A portion of the water 

 was undoubtedly the steam condensed for the performance of the 

 mechanical work, which was very nearly the same in the two cases. 

 Under the head of " The Cost of the Power," are shown the water 

 and coal required for the indicated, the net and the d3'namometer 

 horse powers. The coal required for the several kinds of power, 

 as sliown in the table (lines ?', w and .v), has been calculated from the 

 water (lines 5, t^ u), on the assumption that the engine w\as supplied 

 with steam from a boiler which would uniformly evaporate nine 

 pounds of water per pound of coal. This evaporation is a fair result 

 for a good boiler, and would have been produced by those used in, 

 the experiments, had the feed water been heated as in usual practice, 

 and the evaporation nniformly equal to the result on the second day 

 of the trial. 



The accuracy of all the instruments used was tested either before 

 or after the trials. The scales of the indicators were found to be 

 as follows : 



Itiirht hand instrument 40 pounds per square inch. 



Left " " 37.-4 " " 



The test of the dynamometers was very satisfactory, and was readily 

 conducted by weighing the springs, measuring the distance run by 

 them and the indices, and measuring also the distance from the 

 center of the shaft at which the force was transmitted. 



The meter was tested in place by running water through it into a 

 barrel set on a scale. In these trials the water was so regulated 

 as to pass through the meter at difi'erent velocities, so as to ascertain 

 its )'cUe, or the relation between the amount of water it actually 

 delivered, and that shown by its register. There was no way of 

 ascertaining the position of the pistons inside the meter except by 



