34 Mr. C. Tomlinson on the Motions of certain 



In my first paper on the cohesion-figures of liquids 3 , an expe- 

 riment is described in which creosote was placed on the surface 

 of water in two similar glasses ; but one of them contained one 

 ounce of distilled water, and the other two ounces. The first 

 drop of creosote lasted seven minutes on each surface, the se- 

 cond drop 20 minutes on one ounce of water, 12^ minutes on 

 the two ounces ; the third drop had not disappeared from the 

 first glass after 135 minutes ; but from the second glass it dis- 

 appeared in 25 minutes, and even a fourth drop was disposed of. 



5. Professor Van der Mensbrugghe 4 takes great pains to 

 show that in the experiments a, b, c the ether- vapour streaming 

 down upon the water on the film exerts no mechanical action 

 by its weight. I only referred incidentally to this action, and 

 remarked that a stream of carbonic acid gas from a gas-bottle 

 will, by its mechanical action, produce iridescent rings on some 

 films. The chief action seemed to me to be, as already stated 

 (4), the strong adhesion existing between the water and the 

 ether. The Professor explains the experiments a to /, as well as 

 the varied phenomena of cohesion-figures, on the principle of 

 surface-tension ; and yet, before surface-tension can act in the 

 way described, there must be adhesion. Of course he admits as 

 much, and distinguishes between effects due to various degrees of 

 this force which I have so much insisted on. For example, in § 51 

 of his memoir, in reference to some experiments by the *Abbe 

 Mann 5 , in which whale-oil spreads on the surface of boiling 

 water, while olive-oil and linseed-oil refuse to do so, he says, 

 " This arises most probably from the fact that the first liquid 

 adheres much more strongly to the water than the other two 

 oils, and can thus spread under the action of a force inadequate 

 to the extension of the other two." And again, § 52, with re- 

 ference to the formation of cohesion-figures, he says : — " It is 

 evident that the different oils deposited on pure water cannot 

 produce the same figures, since the phenomenon depends at 

 once on surface-tension and on the amount of adhesion of the 

 substances employed. Hence it is also clear that the same oil 

 may produce different cohesion-figures when placed successively 

 on clean water, mercury, sulphuric acid, &c. This explains per- 

 fectly the numerous varieties of figures described by Mr. Tom- 

 linson." 



6. Connected with these surface-motions is an experiment by 

 Prevost 6 , and one also by Macquer 7 , of which I took note many 



s Phil. Mag. for October 1861. 



4 " Sur la Tension superficielle des Liquides," Mem. de VAcad. Roy. des 

 Sciences Sfc. de Belgique, vol. xxxiv. 1869. 



5 Mem. de VAcad. de Bruxelles, 1780, vol. ii. p. 257. 



6 Ann. de Chim. et de Phys. vol. iv. p. 31. 



7 Diet, de Ch. art. " Verre ardent." 



