dered liquid by watery we conceived that we might be placed 

 in more favourable conditions for elucidating a law. 



fBishop Watson* was the first chemist who endeavoured 

 to estimate the increase of volume when salts dissolve in water ; 

 for, although both Gassendust and the Abbe Nollet:]: had 

 written, and Ellis§ had experimented upon the same subject, 

 they had arrived at conclusions entirely erroneous, which were 

 removed by Watson's more accurate experiments. Watson's 

 apparatus was rude enough, being a matrass capable of hold- 

 ing 67 ounces of water, into which he projected 24 penny- 

 weights of each of the salts upon which he experimented, and 

 noted the rise in the neck of the matrass. He completely ex- 

 ploded, however, the idea that saline substances dissolve in 

 water without increasing its bulk. 



Between the time of Bishop Watson, whose investigations 

 on this subject are most profound, when we consider the 

 period at which he wrote, and that of Dalton, there were no 

 labourers in this field to whom we need draw especial atten- 

 tion. In the year 1840, Dalton || made the interesting dis- 

 covery, that sugar and certain salts on being dissolved in 

 water increase its bulk only by the amount of water pre-exist- 

 ing in them. He generalized this observation by assert- 

 ing that all hydrated salts dissolve in water, increasing its bulk 

 merely by their amount of water of hydration, while anhy- 

 drous salts do not at all increase the bulk of the water in 

 which they are dissolved. 



But it must not be forgotten, that when Dalton published 

 this paper, he was much enfeebled by illness, and on this 

 account it does not derogate from the acuteness of the phi- 

 losopher, that Mr. Holker was unable to confirm Dalton's 

 results in repeating the experiments in 1843**. He did so, 

 however, in the case of sulphate of magnesia, and approxi- 

 matively in that of one or two other salts. As Mr. Holker's 

 paper has not been published, we are unable to state his claims 

 in the progress of this subject; but we believe that an attempt 

 was made to show a multiple relation in the increments of 

 isomorphous salts, although his experiments were conducted 



* Philosophical Transactions, 1770. 



f Gass. Phys. lib. i. sect. 1 . cap. 3. 



\ Lccons dc Physique, vol. iv. § Berlin Memoirs, 1750, * 



II " On the quantity of Acids, Bases and Waters in Salts, and a new niod^fR 

 of measuring them," read to the Manchester Literary and Philosophicaliit 

 Society, 6th October 1840, and published as a pam))hlet. ,,^^- 



** Paper read to the Manchester Literary and Philosophical Society, but ^* 

 not published. [The paper here referred to will be found at p. 207 of th^* 

 present volume of this Journal. — Ed,] 



