Mr. C. Tomlinson on the Cohesion-Figures of Liquids. 253 



pulse outwards. "We thus get a perforated disc : the disc itself 

 is in rapid motion and agitation, but the water seen through the 

 central perforation is tranquil. Both the outer and the inner 

 edges of this disc are perfectly sharp and well defined. The 

 cohesive force of the ether prevents it from breaking up, and 

 even produces a rebound : the disc closes in upon itself, becomes 

 smaller and smaller, still preserving its central perforation and 

 well-defined form, until at length it vanishes under the influence 

 of evaporation, adhesion of the water, and probably electrical 

 action ; or, as is generally the case, the attraction of the sides of 

 the vessel causes the mobile body to disappear by dashing up 

 against the glass. If two or tbree drops be allowed to fall in 

 quick succession, the perforated discs become partially super- 

 posed, but still preserve their distinctive features. (See figs. a } b, c 

 in the sulphuric-ether figure.) 



On placing a drop of rectified ether on the surface of water, it 

 is evident that it has a much stronger cohesion than when adul- 

 terated with alcohol, or rather the water has a less adhesion for 

 it. The drop of ether becomes lenticular, and in doing so dis- 

 charges from all sides a portion of its substance, which assumes 

 the form of a tolerably smooth flat ring : this in its turn dis- 

 charges a portion of ether into the water, which, in seizing it, 

 produces a troubled motion. Hence we have the true ether 

 figure, consisting of a central lenticule, surrounded by a nearly 

 smooth flat ring with radiated markings, and this by an agitated 

 ring with curved markings, as if minute globules of the liquid 

 were diffusing. I have attempted, with the assistance of an artist, 

 to represent this in the Plate. It is tolerably accurate ; but I need 

 hardly suggest that a chemist's eye retains such figures better 

 than an artist's; for to the one they are expressions of natural 

 truths — additional exponents, in fact, of those endless properties 

 which he endeavours to frame into laws; while to the artist 

 these things are mere forms — if beautiful, so much the better — 

 but still only forms, containing no latent truths. 



I may also remark that, in order to get the typical form of each 

 substance, certain precautions are necessary. The water may be 

 distilled ; but this is not absolutely necessary, provided it be che- 

 mically clean. It should be in sufficient quantity to prevent its 

 becoming quickly saturated ; for as the water approaches satu- 

 ration, the figure becomes slightly modified, although it pre- 

 sents the no small advantage of greater persistence. The 

 ether figure will remain for about a second in a nearly sa- 

 turated solution. But what is in many cases absolutely neces- 

 sary to success is, that the glass containing the water be 

 quite clean ; it should be purified from the organic film which 

 covers most matter exposed to the air, by washing it in strong 



