ON STANDARDS OF ELECTRICAL RESISTANCE. 



515 



First Series of Radiation Expenments. 



In applying the preceding Table for the purpose of correcting the results 

 of the thermal experiments, it must be first observed that the external influ- 

 ences on the calorimeter are not zero -n^hen the temperature of the air-ther- 

 mometer coincides -with the indication of that immersed in the calorimeter. 

 This might arise partly from the locality of the two instruments not being 

 the same, but -was, I found, principally owing to the different radiating and 

 absorbing powers of the air-thermometer bulb and of the surface of the 

 calorimeter. Taking, then, the number of instances in which the tempera- 

 ture of the air appeared to exceed that of the water, there are fifteen with a 

 total excess of 259-63, and a resulting gain of temperature of 35-36. Also 

 those in which the air appeared to be colder than the water were five, giving 



a total deficiency of 65-5 with a loss of temperature 4-71. Hence 



259-63 4- 15.r 



4-71 



— f,^ or. J -whence ^7=4-418, which must be added to the indications 

 35-36 



of the thermometer registering the temperature of the air. After this cor- 

 rection has been made, it will be found that the effect of a difference of tem- 

 perature between the air and water, of 9-216, is unity. 



4-418 added to 397-226 gives 401-644 for the corrected temperature of 

 the air in the thermal experiments, and this being 7-238 in excess of the 

 temperature of the calorimeter, the corrected thermal effect -will be 22-0914 — 



7-238 



— -|~- = 21-306, which, after applying the needful correction for the immersed 



9-216 



portion of the thermometer stem, becomes ultimately 21-326. 



The thermal capacity of the calorimeter was made up of 95525 grains of 



distilled water, 26220 grains of copper, equivalent to 2501 grains of water, 



2m2 



