certain Vapours on Films, fyc. 113 



water. Now as these thicknesses vary, for water, from about the 

 0*38 to the 57'75 miliionths of an inch, the film gives all or some 

 of the series of colours known as Newton's rings. In the second 

 place, supposing the drop of oil, &c. to form a coloured film (and 

 most of the turpentine varnishes do so to perfection), the ether- 

 sponge still developes a system of rings, not always beginning with 

 those of the first series, but exhibiting the colours of the second, 

 third, fourth, &c. The diameter of the coloured rings on the oil- 

 film may vaiy from \ of an inch to 2 or 3 inches, and in general 

 they close up and disappear as soon as the ether-sponge is re- 

 moved or gets dry. 



But not only was ether found to produce these effects, but also 

 liquor ammonise, wood -spirit, alcohol, and naphtha, and, as I 

 afterwards found, chloroform, benzole, bisulphide of carbon — in 

 fact any substance that throws off vapour with facility — when a 

 sponge wetted with one of these fluids was held over the film. 

 The effects were not always so good as with ether, but each sub- 

 stance had peculiar features of its own, and no two films of differ- 

 ent oils, &c. exhibited the same phenomena ; indeed the films of 

 the same substance would vary from day to day with varying tem- 

 peratures of the air and other causes. It may be remarked that 

 a sponge wetted with ammonia and held over the film often pro- 

 duced so violent an action as to break it up and scatter it about. 

 It also forms with it a soapy compound which dissolves in the 

 water. Ether-vapour may also produce as violent an action as 

 ammonia. For example, a drop of oil of cinnamon produces on 

 water a mottled film, reminding one of marbled paper. A sponge 

 dipped in chloroform and held over the film, spreads it with a 

 development of colour and incipient rings. The ether-sponge is 

 then powerfully repulsive, spreading, breaking up and scattering 

 the numerous discs into which a single drop of the oil forms. 

 But the ammonia-sponge occasions a remarkable spreading, rapid 

 motion, producing first coloured rings, and then a granular soapy 

 structure, after which all further action ceases, from the filmconi- 

 bining with the water. 



In this way I accumulated a large number of results, which 

 did not appear to throw much light upon the question as to what 

 takes place between ether and water. There seemed to be a 

 repulsive action of some kind, and I tried to measure it by means 

 of a delicately hung torsion-balance of straw, making the straw 

 carry a piece of filtering-paper which was saturated with water, 

 while another piece of paper saturated with ether was brought 

 up near to it ; but I obtained no results in this way. I there- 

 fore tried the action of ether on a thin sheet of water just suffi- 

 cient to cover the surface of clean mercury in a wine glass, or 

 spread over a glass disc 5 or 6 inches in diameter with a ledge of 

 Phil. Mag. S. 4. Vol. 22, No. 145. Aug. 1861. 1 



