Manchester Memoirs^ Vol. xlviii. (1903), No. 3. 17 



about twenty minutes. Direct experiments of the same 

 kind as those of p. 15 gave a difference somewhat greater 

 than this,* 



I have already stated that no result of any value for 

 the weight of ice could be obtained from the apparent 

 weight during immersion. In the case of the copper 

 sphere the volume of included air at the end of an hour's 

 immersion was approximately 0"2 c.c, the actual up- 

 thrust due to ice and air being I"i975 grammes and the 

 upthrust calculated from the weight of the ice being about 

 I '03 grammes. 



The time necessary for attainment of equilibrium of 

 temperature in the ice method does not appear to differ 

 greatly from that required in the method of mixtures 

 (two to three minutes in the case of the objects of Tables 

 I. to IV.). 



In the experiments described in the following 

 paragraphs I used a uniform immersion period of five 

 minutes. 



Variation of Results with the Shape and Mass of the 

 Object. 

 The error due to water included within and weighed 

 with the ice-jacket is naturally larger when the total 

 weight of ice is smaller. This is illustrated by the follow- 

 ing numbers for two leaden spheres weighing respectively 

 37 grammes and 141 grammes : — 





Apparent specific heat. 



Smaller sphere 

 Larger sphere 



•0310 (mean of two not in good agreement). 

 •03035 (mean of two closely agreeing). 



* I do not wish to imply that the volume of water entering the ice-jacket 

 should be equal to the volume of air escaping. It might on the contrary be 

 expected to be rather greater. 



