19.2 Mr. C. Tomlinson on the Cohesion-Figures of Liquids. 



was apparent. The tubes marked Nos. 1-5 contained, — No. 1, a 

 milky, slightly coloured, very limpid fluid ; No. 2, a milky co- 

 lourless fluid, very limpid ; No. 3, a perfectly transparent fluid, 

 limpid; No. 4, an opalescent white jelly, gelatinous camphor in 

 fact, slightly yellow ; No. 5, colourless transparent fluid resting 

 on perfectly colourless jelly. When the whole of the distillate 

 is collected into one vessel, the gelatinous camphor does not 

 appear, it being dissolved in the liquid portion. 



The five liquids thus collected formed as many cohesion- 

 figures. Nos. 1 and 2 resembled the figure of the crude oil ; 

 No. 3 formed a large film, or rather double film, viz. an outer faint 

 one, and an inner thicker one ; the latter opened w T ith a display 

 of iridescent rings, which disappeared when the film was perfectly 

 formed. But no sooner was the film formed than cohesion began 

 to reassert itself, and, adhesion struggling with it, the film broke 

 up, forming a complicated pattern, which played about with a 

 waving-to-and-fro motion so long that the eye became dizzy with 

 looking at it. The disks then expanded and contracted with a 

 display of colour until the whole disappeared. 



No. 4 formed a film covered with a great number of specks of 

 gelatinous camphor, one mass sending off minute globules in radial 

 lines. After a short time a granular disk of camphor w T as formed, 

 and sailed about round by the side of the glass. 



No. 5 formed a film like No. 4, only it almost immediately 

 gave a kind of convulsive start, split into a number of large 

 irregular disks, which continued jerking and splitting and open- 

 ing for some time, as if by a simultaneous movement. 



A drop of the crude oil on water forms a good film with a 

 row of small bosses at the edge, and a row of larger ones just 

 within the edge, — a character that belongs to oil of turpentine 

 and a number of the oils allied to it, of which oil of camphor is 

 one. The film soon opens into well-shaped holes, each of which 

 is surrounded by bosses ; the holes become very numerous and 

 open into each other, forming a kind of network ; and this also 

 breaks up, leaving a few small disks. 



The oil-of-turpentine film presents very distinctive well-marked 

 characters, which qualify it as the representative of a considerable 

 number of oils which are related to it isomerically, and not 

 greatly differing in density ; but the heavier oil of cloves makes 

 an entirely different figure. The moment a drop of the rectified 

 oil of turpentine touches the water, it flashes out into a film with 

 a beautiful display of rainbows. The colour disappears as soon 

 as the film is fairly formed, and the edge becomes marked with 

 a double row of bosses of unequal size, as above noticed. These 

 bosses flatten out into disks, which are surrounded by small dots. 

 A beautiful display of iridescent colours then sets in, beginning 



