19i Mr. C. Tomlinson on the Cohesion-Figures of Liquids, 



in their cohesion-figures. Thus we may compare the oil of bitter 

 almonds with the oils of cinnamon, anise, cumin, &c. On the 

 present occasion, however, I will only notice the oil of bitter 

 almonds. This oil forms a good film with a shadowy outer film, 

 formed by a more fluid and diffusive portion of the oil (an effect 

 by no means rare with the essential oils). The principal film 

 opens into holes, from which shoot out a number of processes 

 like fingers or snails' horns j or, supposing a hole to represent 

 a closed child's hand, and one, two, or three fingers to be quickly 

 opened and shut, we get some idea of the behaviour of the bitter- 

 almond-oil film. Some of the holes send out short processes 

 from equidistant points, thus forming triangles with curved 

 sides : occasionally long processes are shot out, and these in an 

 odd way detach disks of the oil from the parent disk, the final 

 result being the formation of a large number of disks at rest on 

 the surface. These disappear by evaporation and solution with 

 displays of iridescent rings. 



Variations in cohesion-figures, arising from changes in the 

 adhesion-surface, produce interesting results. A drop of water 

 gently delivered to the surface of sulphuric acid from the end of 

 a pipette flattens down into a well-defined disk about the size of 

 a shilling, with radial lines which disappear at the centre, while 

 the fragments remain for some seconds near the circumference. 

 I have obtained three variations of this figure all of the same 

 type, and am preparing drawings of these, and some of the other 

 more striking figures. Alcohol, sulphuric ether, benzole, &c, 

 on sulphuric acid give striking figures, and illustrate the truth 

 of the principle on which these figures are formed, any variation 

 in the adhesive force of the surface being accompanied by a 

 change of figure. * 



When acetic acid is employed as the adhesive surface, a new 

 set of figures is also obtained. Thus oil of camphor, which on 

 water forms a large well-developed film, does not expand into a 

 film at all on acetic acid (sp. gr. 1*045), but forms a small disk, 

 which sails about with considerable agitation, throwing off glo- 

 bules in large number, which are whirled about with great 

 rapidity under the action of the parent disk. This becoming 

 attracted by the sides of the vessel, it will sail round a number 

 of times in contact therewith. 



Oil of lavender on acetic acid also forms a small disk, which 

 becomes greatly agitated, and gathers itself up with strange 

 contortions, thus illustrating in its own way the struggle that is 

 going on between cohesion and adhesion. The oils of cajeput, 

 bergamot, and some others form films on acetic acid with con- 

 siderable agitation, while the oils of cloves and of bitter almonds 

 are quite inert. 



