10 K. HONDA, T. TEE.\DA, Y. YOSHIDA, AND D. ISITANl. 



pdh/lj^Il^ L{a-h,) + v + s,{h-h;)\-P{s,dh,i-s,dJi;) = RdT, 



S.J dh, = — sßh^ . 



EliminatiDg dh^, dJi.., dP, we have approximately 



dh B ^ B 



dT ~ rA f. s. 



P[o(l + A). + .,| '.^^^(1+1) 



If we neglect v in comparison with the volume of the jar, R 

 is equal to Ps^a/T; hence 



dh^ 



It 



■"<i+x) 



In our case, « = 12 cm., r —13. G and 1 + — = 1.26 ; hence at lO'C, 



So 



^ = 0.0025 cm. 

 di 



When the temperature changes, the vapour tension also 

 changes ; but the change of vapour tension per degree rise of 

 temperature in the range of ordinary temperature is about 1/3 

 the change of pressure due to the thermal expansion of air. 

 Hence as the combined effect of these two, we may take 



^ = 0.0033 cm. 

 dl 



We have also experimentally determined this ratio by 

 heating the water in which the jar was immersed, and found 0.004 

 cm., wliich agrees fairly well with the above value. The greater 

 part of the enclosed air, which is in tlie diving jar, is subject 

 to the daily change of temperature by a few degrees of the sea 

 bottom. It is also an easy matter to protect the remaining 

 part of tlie air, from a considerable change of temperature. 



