on the Surface of Water, 535 



cutting it through and through without touching it until it (the 

 acid disk) disappeared. A drop of oil of nutmeg on the water 

 flashed out into a film, completely enclosing the eugenic-acid 

 disk, not touching it, but stopping its motions. The acid disk 

 soon resumed its activity, and shot out small portions of its 

 substance, which skated about in the film with amazing rapidity 

 and disappeared by solution. The acid disk split up into several 

 disks, some of which played about in the film. As this broke 

 up, it formed a large number of small oily-looking disks about 

 the size of a small pin's head. These formed active currents 

 with the eugenic disks, behaving in fact just like the lycopodium 

 powder under similar circumstances. A drop of oil of bitter 

 almonds did not spread at all, but formed a small well-defined 

 lens, which was driven about with vigour by the eugenic-acid 

 disk. 



When a multitude of small fragments of camphor are busily 

 gyrating on water, a drop of eugenic acid gently delivered to 

 the surface arrests their motions ; they become quite inert, and 

 the acid disk makes use of them to form currents, as if they were 

 particles of lycopodium powder. 



Another point of comparison between the eugenic-acid disk 

 and camphor on water is the influence of the air or of evaporation, 

 which in the case of camphor is of even more importance than 

 solution. On a damp day the camphor rotates sluggishly or 

 not at all. The motions are also arrested if the vessel be 

 covered up. It is impossible to produce the beautiful lycopodium 

 currents in a large bottle ; but with the same materials freely 

 exposed to air, the currents are very vigorous, and may be kept 

 up for hours or days*. In such a case the water gets rid of its 

 camphor by evaporation, and the air of the room becomes 

 strongly scented with camphor. Evaporation does not seem to 

 have much effect in maintaining the eugenic-acid motions. The 

 disk will rotate and the lycopodium currents will go on in a stop- 

 pered bottle or in a narrow vessel whether exposed to the air or 

 covered up ; so that solution seems to be the chief force concerned 

 in the eugenic-acid rotations and currents. The high boiling- 

 point of eugenic acid is also favourable to this view. 



The motions and currents produced by eugenic acid on the 

 surface of water may also be noticed in a feebler form if a drop 

 of oil of cloves or of oil of Jamaica pepper be gently deposited 



* These currents are produced, as already noticed, by lowering a stick of 

 camphor vertically into -water dusted faintly with lycopodium. If a piece 

 of filtering paper be tied round a glass rod and the paper be slightly wetted 

 with eugenic acid in the form of a ring round the paper, and this ring be 

 lowered to the surface of water dusted with lycopodium, the currents, in the 

 form of revolving wheels, similar to those of camphor, may be produced, 

 but their duration is comparatively short. 



