446 HENEY A. ROWLAND 



exactly what we should suppo&e, as we have seen that nearly all sources 

 of error tend in the direction of making the radiation too small. For 

 instance, an error came from not stirring the water during the radiation, 

 and there must be a small residual error from not stirring so fast 

 during radiation as during the experiment. Besides this, some parts 

 around the calorimeter were warm during the radiation which were cool 

 during the experiment. And both of these make the correction for 

 radiation too small. However, the error from this source is small, and 

 cannot possibly affect the general conclusions. In each column of 

 Tables LI and LII a dash is placed at the temperature of the jacket, 

 and for fifteen degrees below this point the error in the radiation must 

 produce only an inappreciable error in the equivalent: taking the ob- 

 servations within this limit as the standards, and rejecting the others, 

 we should still arrive at very nearly the same conclusions as if we ac- 

 cepted the whole. 



Most of the experiments are made with a weight of about 7-3 kil., as 

 everything seemed to work best with this weight But for the sake 

 of a test I have run the weight up to 8-6 and down to 4-4 kil., by which 

 the rate of generation of the heat was changed nearly three times. 

 By this the correction for the radiation and the error due to the irregu- 

 larity of the engine are changed, and yet scarcely an appreciable differ- 

 ence in the results can be observed. 



The tables explain themselves very well, but some remarks may be 

 in order. Tables XXXVII to L inclusive are the results of fourteen 

 experiments selected from the total of about thirty, the others not hav- 

 ing been worked up yet, though I propose to do so at nry leisure. 



Table LI gives the collected results. At the top of each column the 

 date of the experiment and number of the thermometer are given, to- 

 gether with the approximate torsion weight and the rate of rise of tem- 

 perature per hour. The dash in each column gives approximately the 

 temperature of the jacket, and hence of the air. There are four col- 

 umns of mean values, but the last, produced from the combination of 

 the table by parts, is the best. 



Table LII gives the mechanical equivalent of heat as deduced from 

 intervals of 10 on Table LI. The selection of intervals of 10 tends 

 to screen the variation of the specific heat of water from view, but a 

 smaller interval gives too many local irregularities. In taking the 

 mean I have given all the observations equal weight, but as the Kew 

 standard was only graduated to -J F. it was impossible to calibrate it 

 so accurately as to avoid irregularities of 0-02C. which would affect 



