1892.] in the neighbourhood of a planet. 319 



Thus the true mean gives 



-=1-063(4 

 P \M 



Laplace makes it 



R .j_ ,Sy_ 



The ratio of the least to the greatest value of p in the formula 

 suggested in this note is 1"149, and Laplace takes the minimum 

 value of p as the radius of his sphere. 



In the case of Jupiter, Laplace's formula gives p = *054 R, and 

 my formula gives p = '0o8R. 



It follows that Laplace's conclusion is sufficiently accurate for 

 the purpose for which it is intended. 



(3) The change of zero of Thermometers. By C. T. Heycock, 

 M.A., King's College. 



The author described the result of experiments he had made 

 in conjunction with Mr Neville to overcome the change in zero 

 which thermometers undergo when heated for a long time. The 

 method consisted in boiling the thermometer for eighteen days 

 in baths of either mercury or sulphur, at the end of this time 

 the zeros were found to be practically fixed unless they were 

 exposed to higher temperatures than those of the substance in 

 which they were boiled. The paper was illustrated by a curve 

 showing that the change in zero was very rapid for the first 

 few hours, amounting in a special case to 11° C. for 20 hours 

 heating, but that afterwards the change became almost nil as 

 the heating was continued. 



(4) The Elasticity of Cubic Crystals. By A. E. H. Love, 

 M.A., St John's College. 



(5) Changes in the dimensions of Elastic Solids due to given 

 systems of forces. By C. Chree, M.A., Fellow of King's College. 



[Abstract] 



This paper deduces from a general theorem due to Professor 

 Betti expressions for the mean values of the strains and stresses 

 in any homogeneous elastic solid acted on by any given system of 

 bodily and surface forces. Formulae for the mean strains in 

 isotropic solids acted on only by surface forces were given by 



