10 Mr. C. Chree on the 



heats of. The first column of relative values is that deduced 

 by Beetz's formula, the second that deduced by mine, taking 

 the conductivity of water as 100. 





Density. 



Conductivity 



relative to 



water; Beetz's 



formula. 



Conductivity 

 relative to 



water, 

 amended. 



NaCl solution 



Ill 

 1-2 

 1083 

 1-496 



1-806 



1-228 



•724 



•804 



1-488 



1-272 



•915 



•691 



103-1 



104-6 



99-1 



97-6 



90-8 



82-1 



112-3 



87-0 



1130 



1239 



64-2 



991 



98-1 

 97-9 

 96-0 

 77-0 



610 



42-3 

 41-9 

 39-1 

 39-0 

 28-2 

 26-0 





Sulphuric-acid solution.. 



_ >> >> ••■ 

 Glycerine 



Ether 



Alrohol 



Chloroform 



Carbon disulphide 



Olive-oil 







These results belong to a temperature of about 11° C. 

 Similar results, answering to a temperature of 32° C, could 

 in like manner be deduced from Beetz's experiments ; but, as 

 already mentioned, they would be less trustworthy, owing to 

 the existence of convection- currents. 



Some very careful experiments on conduction have been 

 carried out by Herr Weber *, who has also made some impor- 

 tant criticisms on previous methods. I shall consider his 

 theory and experiments in connection with a very powerful 

 paper by Herr Lorbergf. This is based entirely on Weber's 

 work, and gives a more exact mathematical treatment of the 

 subject. It also attempts to show that Weber's deductions 

 from his observations require amendment. 



Weber's apparatus consists of two plates of copper, about 

 8 centim. each in radius, whose faces are very accurately 

 plane. During the experiment both plates are exactly hori- 

 zontal, with their centres in one vertical line, and the lower 

 supports the upper by means of three equal symmetrically 

 disposed small pieces of some badly-conducting substance. 

 These keep the plates at a distance of *231 centim. apart. 

 The upper plate is about 1*023 centim. in thickness, and the 

 lower about half as much. The liquid is introduced and 

 maintained between the plates, much as in Prof. Guthrie's 

 apparatus ; only for some of the more mobile liquids Weber 

 had to attach a small glass rim to the lower plate, forming, 



* Wied. Ann. x. pp. 10-3, 304, 472; and xi. p. 347. 

 f Ibid. xiv. pp. 291 & 427. 



