Skey. — On the Movements of Camphor on Water. 477 



camphor are the effect of electrical reactions, but that this is not so appears 

 from the fact that neither of the poles of a six-pair Grove battery, in full 

 action and in good working order, at all effects these movements when 

 applied close to the camphor. The poles were pointed in order to be in the 

 most favourable condition for effect. 



The ground being thus cleared, it remains for me to tender for your 

 approval a theory which, in my opinion, explains the phenomena in 

 question. This I will do, and along with it I will describe or demonstrate, 

 as the case admits, the experimental results upon which, in conjunction 

 with those related above, this theory is based. 



You wiU perhaps remember that in the introductory part of this paper 

 Is tated to you the well-known fact that, for the exhibition of the movements, 

 which I now desire to explain, it is necessary to have the water-surface free 

 from oily matters. Now a knowledge of this is highly suggestive ; it is as 

 you will find the key to the question before us. A drop of oil (as you 

 observe) stops in a peremptory manner all camphor movements, and it 

 is now our proper course to enquire how it effects this. It can only, so 

 far as I see, effect this in two ways, either by enfilmning the camphor 

 and so preventing evaporation, or it is not as a suspensive medium favour- 

 able to the continuance of such movements ; thai this last is the case is 

 shown by the following experiment. 



I float a small piece of cork upon turpentine, on this cork I place 

 camphor, and you observe that we get no camphoric movement.* Clearly 

 then it appears that whether we are to get the phenomena or not 

 depends upon the nature of the surface of the liquid which we use for 

 flotation, and this independent of any effect it may have upon the solid 

 camphor in preventing its evaporation. The knowledge of the fact that 

 oils generally are, in this particular respect, antagonistic to camphor- 

 movements I sought to amplify, and in this I have succeeded. Thus I 

 find that besides them alcohol, ether, bi-sulphide of carbon and ammonia, 

 applied even as vapours, and only in minute quantities, arrest camphoric 

 movements very quickly. I further find that such movements are very 

 much less rapid and prolonged if the water used is charged heavily with 

 either acids or salts. f 



Being thus acquainted with the fact that so many and such diverse sub- 

 stances as those just above cited, render water unfavourable for camphoric 



* This fact, by the way, is corroborative of the correctness of the opinion I have 

 ventiired above, viz., that camphor movements are not caused directly by the impinge- 

 ment of its vapour upon the liquid which floats it. 



t I have since found that, in singular opposition to these vapours, etc., gasoline not 

 only refuses to stop or retard camphoric movements, but even starts them in case of 

 camphor rendered stationary in this way. 

 t 



