20 Mr. Graham on Exceptions to the Law 



y is multiplied on the right-hand side, being equal to unit. 

 But the theorem alone, without considering the nature of the 

 development, cannot be a proper foundation for this doctrine ; 

 it does not put the analyst in possession of the true principles 

 of the method. All the difficulties, and, I may add, a great 

 part of the celebrity of this kind of investigation, have arisen 

 from the manner in which it has been presented to the public. 

 I have no room left to add any thing respecting the equi- 

 librium of fluids. From what you say, I apprehend there is not 

 much between us. It would greatly contribute to throw light 

 on this subject if any one would attempt to demonstrate syn- 

 thetically Laplace's proposition, namely, That a homogeneous 

 planet in a fluid state, will be in equilibrio, when the resultant 

 of the accelerating forces acting upon a particle in the surface 

 is perpendicular to that surface. I am of opinion he would 

 be forced to adopt my conditions of equilibrium, in which case 

 the task is easy ; but I maintain that it is impossible he could 

 prove any thing contrary to them. I have the honour to be, sir. 



Your obedient servant, 

 June 12, 1827. J- IvORY. 



IV. Ofi Exceptiojis to the Law that Salts ai-e more soluble in 

 hot than in cold Water ; with a new Instaiice. By Thomas 

 Graham, M.A. * 



T^HE bodies which have been observed to possess this ano- 

 -*- malous solubility are the hydrate of lime and the sulphate 

 of soda : its detection in the flrst case we owe to Mr. Dalton, 

 and in the latter to M. Gay-Lussac. The phosphate of mag- 

 nesia, a body like the hydrate of lime of sparing solubility, 

 appears from our experiments to belong to the same class. 



To form phosphate of magnesia, phosphate of soda and 

 sulphate of magnesia in crystals were separately dissolved in 

 water, in the proportion of 21 parts of the former to 15'375 

 parts of the latter, or of an integrant particle of each. These 

 solutions were mixed and set aside. Within twenty-four hours 

 the phosphate of magnesia had precipitated, generally in tufts 

 of short acicular crystals, while sulphate of soda remained in 

 solution. According to Dr. Thomson this salt is composed of 



One atom phosphoric acid 3*5 



One atom magnesia 2*5 



Seven atoms water 7*875 



1 3-875 

 Communicated hy the Author. 



It 



