120 On the Action of certain Vapours on Films, &;c. 



ether were shaken up together and poured out into a small 

 porcelain dish ; the surface was dusted with lycopodium, and 

 the ether-sponge presented to it: there was no action; the powder 

 was not displaced or disturbed. The solution of ether was then 

 boiled and filtered, and, when cold, the surface was again dusted 

 with the powder. The ether-sponge now produced a repulsion 

 of the powder, not so decidedly as with plain water, but still a 

 good repulsion. 



The solution of ether was also made to carry an oil-film. A 

 drop of varnish formed an exquisite series of coloured rings, 

 and the ether-sponge also displayed some very beautiful rings ; 

 but after a minute or two, when the adhesion between the solu- 

 tion and the film was complete, the ether-sponge was power- 

 less. 



It may also be mentioned that a vapour acts differently on 

 the film according as it has a greater attraction for the water or 

 for the film. If it has a strong attraction for the water, it will thin 

 out and disperse the film. If its attraction is strong for the film, 

 it will gather it up, thicken it, and deprive it of colour. Thus 

 with a film of oil of lavender the ether scatters and disperses, 

 while the benzole sponge thickens and attracts; in fact the 

 benzole vapour condenses into little discs, which unite with 

 the film. So also if a drop of oil of peppermint be placed on 

 water, it spreads out into a honeycombed film displaying colour. 

 If the ether-sponge be presented, the vapour pours down in a 

 cataract and powerfully displaces the film (a very common effect 

 of ether-vapour on films of the essential oils) ; whereas, if the 

 turpentine sponge be held over it, the scattered parts of the 

 film sail up to it, gather themselves together, and form a num- 

 ber of thickening lenticules. 



I do not like to intrude further on your patience at present. 

 Should this letter not disappoint the interest you have kindly 

 expressed in this inquiry, I will trouble yoxi with a second, and 

 in the mean time subscribe myself, 



Your attached friend, 



Charles Tomlinson. 



King's College, London, 

 June 22, 1861. 



