Sxzv,— 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 i 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 will 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; that 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 camphorie 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. 
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 
ventured 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 camphorie movements, but even starts them in case of 
camphor rendered stationary in this way. 
