certain Vapours on Films, fyc. 115 



with spirits of wine, saline solutions, and even mercury. I 

 changed the nature of the hot surface, and found that ether 

 would roll about on hot mercury, hot oil, and hot water. I 

 also found it perfectly easy to place a drop of water on rape or 

 olive-oil heated to about 400° or 500°. All that was necessary 

 was to deliver the water gently from a dropping-tube to the oil 

 without any fall or splashing ; it would then roll about for a 

 considerable time. If ether were also placed on the hot oil, it 

 would unite with the water and form a shell about it. 



When M. Boutigny showed his remarkable experiments in 

 your laboratory in 1845, you informed him of my results, and 

 he admitted that they were quite new to him. 



On trying some of the fixed oils on the surface of hot water 

 and mercury, turpentine on hot sulphuric acid, &c, the single 

 drop used for each experiment either became spheroidal, or flat- 

 tened into a disc, the latter rotating on a vertical axis. Experi- 

 ments of this kind were connected in my mind with the motions 

 of camphor on the surface of water, as well as the agitation of 

 ether and other liquids. I tried the effect of various vapours on 

 camphor while rotating on water ; and the results first suggested 

 to me what I think is the key, if not the master-key, to these 

 experiments; for, as I shall hereafter endeavour to show, elec- 

 tricity has some share in these results. A pellet of sponge 

 saturated with benzole held over a rotating piece of camphor, 

 had the effect of increasing the rotations of the smaller frag 

 ments to such an extent that the form of the camphor often 

 became quite indistinct, and appeared as a mere cloudy haze. 

 After an experiment of this kind, the morsel of camphor displays 

 one or two brilliant points where the structure is altered and the 

 light abundantly reflected. These points are the effect of solu- 

 tion. The benzole vapour seizes the camphor and begins to dis- 

 solve it ; and during this action there is a contest between the 

 cohesion of the camphor and the film formed by the condensed 

 vapour of benzole, and the diffusive tendency of the water : there 

 is a contest, in fact, between cohesion and adhesion. The forma- 

 tion of this film about the camphor may be plainly seen by 

 holding another sponge dipped in chloroform instead of benzole 

 over camphor : it first produces a rapid spinning, the effect 

 of solution; but nearly as fast as the solution is formed the 

 camphor is displaced by the water, and a solid opake crust of 

 camphor is formed. Bisulphide of carbon held over the spin- 

 ning camphor drives it about ; and when a drop of that sub- 

 stance is placed on the water, it does not arrest the motions of 

 the camphor, but follows it about. Persian naphtha causes the 

 camphor to spin more rapidly; and a drop of that substance 

 placed on the water will pursue the camphor with great swift- 

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