L'L* Dr. < '. l.'lnvr. / I on 



effects HIOO, &C., with the additional battery resistances 100, &c., are a 

 very fair approximation to the truth. There seems little doubt that 

 with a fresh dry cell the reading at the steam point is raised fully the 

 hundredth of a degree, even with 100 ohms in the Iwittery circuit. If 

 20 ohms only were inserted, the heating effect would amount to nearly 

 two-tenths of a degree. In this latter event, an increase of 5 ohms in 

 the battery resistance would lower the observed value of Rj by about 

 0-06 C. 



$ 20. We have next to consider the relative values of the heating 

 effects at the three fixed points. These have been determined by a 

 series of special determinations of the values of HSO r- HJOO- During 

 the majority of the experiments the battery resistance was approxi- 

 mately constant, and not far from 5 ohms. The following table 

 gives the observed values of the ratios 



(H-20 - HI oo at steam point)/(Hjg - HIOO at ice point) 

 and (H->o - HIOO at sulphur point) (H 2 o - HIOO at ice point) 



for the several thermometers, as well as the values calculated from 

 Table VII for the ratios of the heat supplies. 



Table IX. Differential Heating Effects at Ice, Steam, and Sulphur 

 Points (found experimentally). 



The table is based on eighteen experiments comparing the (steam/ice) 

 ratios, and eight experiments comparing the (sulphur/ice) ratios. In 

 most cases the several steam/ice observations with the same thermometer 

 showed a remarkably good agreement, but the results with K 5 and K- 

 were less harmonious than the others. The sulphur/ice observations 

 were so few that little weight attaches to the results for the individual 

 thermometers ; but the final mean should not be much in error. The 

 highest value of the sulphur ice ratio observed was 0*42 in the single 

 experiment made with K 5 . A considerable number of heating experi- 

 ments have been made in sulphur, but I have employed in Table IX 

 as in the case of steam only those which were made on the same day 



