404 Biographical Sketch of [June 



subject. Let it be remembered, however, that the late Dr. 

 Johnstone, of Worcester, recommended the use of muriatic acid 

 vapour for this very purpose in the year 1756, and had probably 

 repeatedly made use of it in private practice, and in the prison 

 and hospital of that city, some years before its first application 

 by M. Morveau. 



The other paper of M. Morveau, already alluded to, has for 

 its object the relation of experiments made to verify Dr. Brook 

 Taylor's method of measuring the adhesion of surfaces. 



James Bernouilli, in his dissertations on the weight of the 

 atmosphere, published in 1682, maintains that the resistance 

 which two pieces of polished marble oppose to their separation 

 is owing to the pressure of the air. This, however, was dis- 

 proved experimentally in 1713 by Hawksbee ; and about the 

 same time Dr. Brook Taylor, having observed the ascent of 

 water between two planes of glass, was induced to make several 

 experiments on the adhesion of surfaces, from which he con- 

 cluded, that the degree of this force might be measured by the 

 weight required to separate them. Nevertheless, in 1772, 

 MM. Lagrange and Cigna, taking for granted a natural repulsion 

 between water and oily substances, imagined, if there was any 

 adhesion between water and a plate of tallow, that it must be 

 occasioned by a cause different from attraction. The reality of 

 the adhesion being then ascertained, they concluded that it must 

 be occasioned by the pressure of the air, and, therefore, that 

 Dr. Taylor's theory was unfounded. 



Such was the state of opinions on the subject when M. Mor- 

 veau's memoir made its appearance. In this paper, he shows 

 first, that water will ascend between two plates of tallow sepa- 

 rated from each other -i of aline, and in circumstances in which 

 the pressure of the air does not appear to have any influence ; 

 secondly, he suspended a small polished disk of glass to one 

 arm of a balance, and brought it in contact with a surface of 

 mercury ; then, by adding weights to the other arm till the disk 

 separated from the mercury, he ascertained the adhesive force 

 between these two substances ; the same apparatus being 

 transferred within the receiver of an air-pump, and a vacuum 

 being produced, precisely the same results as before took place ; 

 hence the truth of Dr. B. Taylor's theory was satisfactorily esta- 

 blished. In the subsequent part of the memoir, M. de Morveau 

 appears in the higher character of an original discoverer. He 

 observed that the same disk of glass which, when in contact 

 with pure water, adhered tp it with a force equal to 258 gr. 

 required a counterpoise of only 210 gr. in order to separate it 

 from a solution of potash, notwithstanding the superior density 

 of this last. No adequate cause for the difference of these 

 results presenting itself, except the difference of chemical affinity 

 .between each fluid and the glass, M. de Morveau was encouraged 

 to undertake some other experiments in the hope of adapting an 



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