104 DR seller's memoir OF THE 



concretions out of the body; but he did not attempt to administer these remedies 

 internally, till he learned Whytt's method, as described in his first paper. 



A great part of Whytt's treatise is taken up with the investigation of the 

 chemical character of lime-water, a subject, particularly at the time when the 

 original paper was published, very little understood. In the third edition he 

 takes the opportunity of stating how much light had very recently been thrown 

 on the chemical relations of lime by the discoveries of Dr Joseph Black, then 

 Professor of Chemistry in the University of Glasgow. Whytt now understood 

 the change produced on limestone and shells by fire ; also why quicklime by 

 exposure to air loses its acrimony, and becomes insoluble in water ; again, why 

 lime-water by the same exposure throws up an earthy crust and loses its solvent 

 virtues. 



In the " Edinburgh Essays, Physical and Literary," of date 1750, Whytt pub- 

 lished a paper on the various strength of different lime-waters. This paper, 

 which is reprinted in the edition of his works edited by his son, was occasioned 

 principally by objections raised by his colleague Dr Alston, Professor of Materia 

 Medica, to some of his statements regarding lime-water. The controversy be- 

 tween the two professors is worthy of a short notice, were it for no other purpose 

 than to add to the many examples, showing how insuperable, in things afterwards 

 found to be most simple, the obstacles to discovery continue to be, so long as the 

 true principle applicable to the case is unknown, as well as how much instruc- 

 tion is contained in the study of such impediments when once overcome. It 

 seems to the present age almost incredible, that ingenious trains of experiments 

 and long dissertations should have been necessary to settle such points as how 

 much more soluble in water oyster-lime is than stone-lime, how much double 

 lime-water exceeds single in strength, or why lime-water made in close vessels is 

 more powerful than that made in open vessels. Whytt and Alston, in common 

 with the whole chemical world at that era, did not expect to dissolve any quan- 

 tity of lime, however small, by throwing on it any quantity of water, however 

 great. They did not believe lime-water to be a mere solution of lime, but held it 

 to be a liquid formed by the impregnation of water with certain virtues derived 

 from the lime. Whytt regarded oyster or cockle shell lime-water as stronger 

 than stone lime-water, resting this inference on the irrefragable proof, that the 

 specific gravity of the former is greater than that of the latter. It were super- 

 fluous to trace out the particular sources of the discrepancy of opinion between 

 the two professors. It does not appear, however, to have occurred to chemists of 

 that period, till Black took up the inquiry, that what they called lime contained 

 insoluble foreign matters, or that the water employed was not always of the same 

 purity, or that it was necessary to attend to the variation of temperature in their 

 several experiments. Yet this controversy between Whytt and Alston proved 

 the immediate cause of most important results. In the interesting account which 



