Mr. C. Tomlinson on the Cohesion-Figures of Liquids. 189 



oil on C formed a small film thick and bossy ; after some minutes 

 it spread somewhat wider, and produced the pattern in a sluggish, 

 imperfect manner. It was, however, instructive as showing 

 more clearly the mode in which this complicated pattern pro- 

 pagates itself. After about twenty minutes a third drop on C 

 did not spread at all, but remained lenticular. 



A second drop of oil on B acted well, but more slowly than 

 the first. A third drop after some minutes scarcely acted at all, 

 showing that adhesion was nearly satisfied. 



The effect of the larger volume of water in favouring solution 

 was shown in D. This surface received a second, a third, and a 

 fourth drop, and each of the resulting films displayed the pattern 

 admirably. When a fifth drop was added, the film was thick 

 and bossy, but the pattern set in and continued to play slug- 

 gishly about for some time. 



Similar trials were made with oil of bitter almonds and oil of 

 spike, with somewhat similar results, varying, however, with the 

 solubility of the oil. A fixed oil was also tried. A drop of 

 castor oil on the plate B, in the very act of spreading, was 

 attracted to the side, so that the figure was marred. The figure 

 was very fine on C, but finest on D, the enlarged surface favour- 

 ing the phenomena of this film, namely, a large shadowy outer 

 film, within which is a very wide perforated border, with a 

 beautiful lace-like pattern*, then a charming series of Newton's 

 rings bounding a smooth colourless centre. 



The cohesion-figure of balsam of copaiba, with its broad lus- 

 trous iridescent rings and sharply defined outer edge, shows 

 wondrously well on the surfaces B, C, and D ; but perhaps the 

 colours are most lustrous on the smaller surface C. 



There are other circumstances which modify the cohesion- 

 figures of liquids. The cohesion-figure of a volatile oil, for ex- 

 ample, is liable to certain variations, according to its density and 

 some other circumstances. The figure in its main features may 

 be produced so as to be easily recognized, from various speci- 

 mens of oil, all differing somewhat in physical constitution, 

 that is, supposing them to be pure. Thus the oil-of-lavender 

 pattern may vary somewhat in different specimens, since it varies 

 in density from 087 to 0*94. Its cohesion-figure may be more 

 minute in the oil of one season, or of one maker, than in that of 



* I stated at the British-Association Meeting at Manchester during the 

 reading of ray first paper on this subject, that many of these cohesion-figures 

 are calculated to give hints to the pattern-designer. I have shown these 

 figures to artists, who pronounce some of them to be " perfect beauty," and 

 agree with me that numerous shawl and other patterns, fringes and borders 

 of great novelty and effect, both as to form and colour, might be got up 

 from a study of these figures. 



