Sxey.—On the Movements of Camphor on Water. 479 
First then in regard to the nature of this modification. Camphor, I 
should remind you, has properties affecting this question as follows :—It is 
soluble in water, and so without doubt combines with it; it is not decom- 
posed by water, even in conjunction with air that is at common temperatures, 
and it is a resin slowly volatile at such temperatures. 
Now camphor, as we have seen, modifies a very much larger extent of 
surface when placed in contact with water than when suspended over it. 
We may, therefore, be certain that the modification in question is not 
occasioned simply by a deposit of condensed camphor vapour upon the 
water surface, but rather by some combination of it with water. This 
combination, however, is not that which is obtained by saturating water 
with camphor in the ordinary way (a compound containing one part of 
camphor to one thousand parts of water), as is shown by the fact I have 
already stated to you, that a saturated solution of camphor in water allows 
camphor to describe movements upon its surface; this compound, therefore, 
is one new to us, it can only exist as a thin surface film, and is therefore 
doubtless one far richer in camphor than that which we already know of, 
a compound indeed so highly camphoretted that it, in all probability, 
partakes in an eminent degree of the characters of an oil.* However, it is 
impossible for me as yet to obtain direct evidence as to the nature of a film 
so exceedingly thin as this. We must therefore for the present rest content 
with the indirect evidence which we now have. 
Granted, then, that the modification effected upon a surface of water by 
camphor is owing to a combination of the two for the production of a highly 
camphoretted oil, I have only now to show the precise manner in which 
this compound induces camphor to move. 
For this purpose I will refer you to the effect which a drop of oil has 
when placed upon water laden with an indicatory substance, such as clay 
in fine particles; the oil spreads quickly and regularly around, and in the 
act urges the clay to the side of the containing vessel, where it becomes 
stationary. Now the clay and the oil here are, I hold, fairly representative 
of the camphor and its oily compound; there is this difference, however, in 
the movement of the oils, and it is an important one, it is a difference upon 
which all camphor movement depends,—the spread of oil in the case of 
camphor is not even around it, as is that of the other oil; were it so there 
would be no such phenomenon as that we are investigating. Regularity of 
spread is in this case impossible, because the production is irregular, owing 
to the highly crystalline nature of camphor, and its great fragility, whereby 
* I have lately observed that water thus modified, when compared side by side 
with pure water, exhibits a higher lustre than the pure water does, a fact greatly in 
favour of this view, 
