300 



Mr. C. Chree. 



[Apr. 21, 



this when the temperature is constant, agrees with the above 

 expression if p = q = r = s. 



We see that the state of equilibrium will vary rapidly with the 

 temperature if H be large, that is, if the chemical process is attended 

 by the evolution of a large quantity of heat. 



The effect of alterations in the external circumstances such as 

 those which may be produced by capillarity, pressure, or electrifica- 

 tion are investigated, and it is shown that anything giving rise to 

 potential energy which increases as the chemical combination goes on 

 tends to stop the combination. 



The last part of the paper is taken up with the consideration of 

 irreversible effects such as those accompanying the passage of electric 

 currents through metallic conductors or electrolytes. These are 

 looked upon as the average of a large number of discontinuous 

 phenomena which succeed each other with great rapidity. The 

 ordinary electrical equations with the usual resistance terms in, 

 represent on this view the average state of the system, but give no 

 direct information about its state at any particular instant. It is 

 shown that if we take this view we can apply dynamical principles to 

 these irreversible effects, and the results of this application to the 

 case of electrical resistance are given in the paper. 



V. " Conduction of Heat in Liquids." By C. Chree, B.A., 

 King's College, Cambridge. Communicated by Professor 

 J. J. Thomson, F.R.S. Received March 31, 1887. 



(Abstract.) 



In this research the liquid layer through which the conduction 

 takes place is of a moderate thickness, the object being to obtain 

 results not open to the objections which can be raised against most 

 previous methods, in which conduction has taken place through 

 layers of very small thickness. 



Two similar forms of apparatus, differing chiefly in size, were 

 employed, but from the larger apparatus few results were obtained, 

 and to these little independent weight is assigned. 



The liquid was contained in a wooden tub, and heat was applied 

 by pouring hot water into a metal dish supported so as to be in con- 

 tact with the liquid surface. At a given depth was fixed a tine 

 platinum wire, and the variation in its temperature was determined 

 by observing the variation in its electrical resistance. By this means 

 the temperature at a given depth in the liquid is determined for any 

 instant subsequent to the application of heat. 



In applying the heat a given quantity of water, heated to a given 



