44 



Mr. C. Chree. 



Neither the method nor the theory is so extremely accurate that 

 any value can be attached to the third significant figure in the value 

 for k in assigning absolute values for the conductivity. In assigning 

 relative values, the third figure would have some weight in liquids in 

 which the heat was applied so similarly as in the case of water and 

 the above solutions. Since, however, the temperatures of the experi- 

 ments were not identical, and the conductivity unquestionably in- 

 creases with the temperature, it would probably be unsafe to deduce 

 from the above numbers any more precise conclusion than that the 

 presence of a very considerable quantity of sulphuric acid produces 

 an extremely small change in the conductivity for heat of water. 



It might also be considered almost certain that the time at which 

 the temperature was rising fastest diminished as the density of the 

 solution increased. This signifies that the velocity with which heat- 

 waves travel, or the temperature conductivity of Weber, is greater the 

 stronger the solution. The liquid in the tub in these experiments 

 was in general stirred up fifteen minutes after the heat had been 

 applied. It is pretty obvious that the ratio of the galvanometer 

 reading after the stirring to that before should diminish as the 

 temperature conductivity increases. The ratios so obtained for water 

 and the above solutions were in order, 1*36, T34, 1*32, 1*28 and 123. 



No very great accuracy can be claimed for these numbers as the 

 determination was somewhat rough, but as independent evidence of 

 the truth of the above statement as to the temperature conductivity 

 they are of considerable weight. 



For bisulphide of carbon, methylated spirit, and paraffin oil, the 

 values from Tables I and II substituted in equation (7) lead to the 

 following results : — 



Table IV. 











Mean 





Mean 



Liquid. 



X. 





TT. 



value 



Tc. 



tempera- 











of X. 





ture. 



Bisulphide of carbon. 



16-5 



-10- 



4 x 36 -16 









16 -6 



-10- 



4 xl5 



16 66 



-0322 



15*° 





16-7 



+ io- 



4 x 9-26 









Methylated spirit. . . . 



27 5 

 27'6 



-10- 

 -10- 



4 x 26-5 

 4 x 13 -8 



27-566 



0-0354 



19| 





25 -8 



-10- 



4 x 18 -66 



25-88 



-0264 



19 





26 -0 



+ 10" 



4 x 26 -66 



There still remain to be considered the experiments in which the 

 water was not siphoned from the dish. As an example of the ap- 



