HENRY A. ROWLAND 



proved in two ways; first, by the use of a motive power more regular in 

 its action; and, second, by a more exact determination of the loss due to 

 radiation. The effect of the irregularity of the engine has been calcu- 

 lated as about 1 in 4000, and I suppose that the error due to it cannot 

 be as much as that after applying the correction. The error due to 

 radiation is nearly neutralized, at least between and 30, by using 

 the jacket at different temperatures. There may be an error of a small 

 amount at that point (30) in the direction of making the mechanical 

 equivalent too great, and the specific heat may keep on decreasing to 

 even 40. 



Between the limits of 15 and 25 I feel almost certain that no sub- 

 sequent experiments will change my values of the equivalent so much 

 as two parts in one thousand, and even outside those limits, say be- 

 tween 10 and 30, I doubt whether the figures will ever be changed 

 much more than that amount. 



It is my intention to continue the experiments, as well as work up 

 the remainder of the old ones. I shall also use some liquids in the 

 calorimeter other than water, and so have the equivalent in terms of 

 more than one fluid. 



Baltimore, 1878-79. FinisTied May 27, 1879. 



