Skey, — On the Movements of Camphor on Water. 405 



Professor's theory, and I now proceed to furnish you with an account of 

 the results which I have obtained by the prosecution of the experiments 

 which, as stated, I have been induced to make. 



Now Mr. Casamajor states the fact, among others, that citric, benzoic, 

 and carbohc acids resemble camphor in their ability to move upon water, 

 and so pursuing this I have ascertained the following facts : — 



1. That citrate of potash, acetate of potash, succinate of ammonia, and 

 albumen dried at about 100° F., also describe movements upon such a 

 surface.* 



2. That the purer the water is as regards matter dissolved therein, the 

 freer as a general rule these substances, as also camphor, move thereon. 

 Thus camphor or citric acid, both very free movers upon pure water, either 

 refuse to move, or move but slowly and in a confined manner, upon water 

 saturated with carbonate or borate of soda, or with chloride of sodium. 



3. That none of these substances are able to describe movements upon 

 a solution of albumen in water if it contains more albumen than one in a 

 thousand parts of solution ; nor yet upon weak gum-water ;f indeed, so un- 

 favourable is gum-water to movements of this kind, that a mixture of one 

 of gum to four of water refuses to allow olive oil to spread thereon, and 

 allows even gasoline to move but slowly. 



4. That white of egg or gum-water applied as a drop to water on which 

 camphor is moving, peremptorily stops it ; — spreading as it does on the sur- 

 face like oil, it behaves like it in respect to the movements described. 



A consideration of these facts, especially as they relate to camphor — a 

 substance which I take to be typical of the rest — shows in the first place, 

 that water when combined with saline matter to a large extent is (although 

 still in a liquid state) not favourable to the movement of camphor thereon. 

 It is seen therefore that, for such movement to be of the liveliest, water in 

 a free state or comparatively free state is requisite, consequently that the 

 first essential for movement is a combination of camphor with water— a con- 

 dition which you will remember I insisted on as necessary for such purpose. 

 In the second place, it is seen that, while solution plays a necessary part in 

 these phenomena, mobility of the sustaining liquid plays another. It is seen 

 that water containing a little gum or albuminous matter refuses to allow 

 camphor, etc., to move thereon ; and this is clearly due to the greater viscosity 

 of the mixture over that of water. But though viscosity, as a property of the 

 sustaming liquid, is thus unfavourable to movement, it appears to be neces- 



* Acetate of potash or of lead gives no movement thereon. Cochineal, a substance 

 composed of various principles, moves also. 



t Healthy urine, owing to the gummy matter dissolved therein, has to be diluted to 

 foiu' or five volumes with water before it allows camphor to describe movements thereon. 



