384 Mr. C. Tomlinson on the Motions of Camphor 



19. Considering the mode in which surface-tension acts, it will 

 naturally be supposed that the motions in question are not con- 

 fined to camphor and a few other solids, nor to creosote and 

 a few other liquids. In fact fragments of any body that act by 

 suddenly lowering the surface-tension at the spot on which they 

 fall are liable to these camphor motions. Many salts act in this 

 way, the last that I have observed being sulphate of aniline. The 

 following solids also rotate : — Borneol, naphthol, thymol, nitro- 

 toluol : this was inactive on water at 56° F,, but very active on 

 water at 90°, a crystalline needle sweeping over the surface at 

 right angles to the length of the crystal. Binitrotoluol on water 

 at 96°. Hydrochlorate of toluidin : a crystalline fragment 

 darted to and fro in short jerks, as if surprised at the novelty of 

 its situation, and then, accepting the conditions, moved rapidly 

 over the surface in circular sweeps and quickly disappeared. 

 Acetamid behaved in a similar manner. Lactid and oxamethan 

 also rotate rapidly. Sulphaldehyd rotates rapidly in wide sweeps 

 and soon becomes motionless. The same phenomena are exhi- 

 bited by benzoic anhydride. Amidobenzoic acid also rotates 

 rapidly, and quickly disappears ; while the crystalline portion of 

 nitrobenzoic ether sails round and round near the edge, and con- 

 tinues to do so for a long time. 



Among liquids, a drop of toluidin on the surface of water, in 

 a vessel 4 inches in diameter, affords an instructive illustration 

 of surface-tension : the drop forms a figure for an instant some- 

 thing like that of creosote ; it then bursts as with an explosion, 

 dotting the whole surface with smaller figures, each of which 

 also explodes ; and the smaller particles resulting therefrom ra- 

 pidly disappear amid lively agitations. A drop of phenyl-mus- 

 tard oil quickly spreads into a large ragged film, which is torn 

 into numerous fragments, covering the surface ; and then each 

 fragment gathers itself up into a well shaped lens. A second 

 drop rests as a lens. A drop of monochloracetic ether spreads 

 rapidly over the surface and rebounds to the centre, breaks 

 up into numerous ovoid masses, with colour, which rapidly dis- 

 appear with a remarkable opening out. When the whole has 

 disappeared, the motes on the surface rush wildly to and fro. 

 Formiate of ethyl produces a very pretty rose-engine figure with a 

 central boss. Oxalate of ethyl forms a wide film with iridescent 

 edges, and then, in waving figures, quickly disappears. Iodide 

 of allyl gives a colourless film over the whole surface, then ex- 

 hibits a magnificent display of iridescence, breaks up and in- 

 stantly disappears. The following liquids also present interest- 

 ing phenomena : — Nitrobenzol, nitrobenzoic ether, nitrotoluol, 

 and cymol. It would be easy to extend the list both of solids 

 and liquids that afford instructive illustrations of surface-tension, 



