Mr. C. Tomlinson on the Cohesion-Figures of Liquids. 257 



formation, holes open near the edge, starting into existence and 

 altering rapidly, and the film separates into a kind of network 

 and two or three well-defined flat discs. 



When a drop of oil of olives is placed on water, the first thing 

 that strikes the eye is a beautiful widening rainbow, which seems 

 to deposit the film and then disappear. The film itself is colour- 

 less, and it has an indented edge displaying a very light and 

 elegant kind of lace-pattern, similar to what,' I believe, is called 

 guipure, in which a raised thread traces the outline. (Plate IV.) 

 After a few minutes the pattern vanishes, and the oil collects into 

 an irregular trail with ragged edges, surrounded by numerous 

 small globules. 



A drop of oil of almonds on water spreads into a large film 

 with a beautiful lace-like edge, which soon disappears by the 

 holes opening into each other. (See Plate.) The edge separates 

 from the parent film, and forms small lenticules outside it. The 

 edge of the film appears a little raised ; the holes in it continue 

 to open and widen, and the detached pieces shrink up into lenti- 

 cules ; and in a few minutes the parent film has diminished to 

 the size of a shilling, surrounded by a number of lenticules of 

 various degrees of smallness. 



Now when olive oil is used to adulterate oil of cinnamon, its 

 presence may be detected by some of the characters which the 

 oil-of-olives film exhibits alone, and especially by its iridescence. 

 I added one drop of oil of olives to ten drops of oil of cinnamon ; 

 and the film formed by one drop of the mixture on water exhi- 

 bited the following characters : — 1st. A display of beautiful iri- 

 descent rings, which shrank into angular masses and so disap- 

 peared. 2nd. A considerable portion of the film gathered itself 

 up into a central disc about the size of a wafer. 3rd. This disc 

 was surrounded by a delicate perforated silvery film which quickly 

 evaporated, leaving some minute lenticules which became fringed 

 with a kind of frill. And then, 5th. These lenticules exhibited 

 minute systems of iridescent rings. These iridescent effects at 

 the commencement and close of the observation do not belong 

 to oil of cinnamon, but are characteristic of oil of olives. These 

 and the other phenomena are sufficient to detect the presence of 

 a small portion of oil of olives in oil of cinnamon. By increasing 

 the proportion of the adulterating oil, the properties of the oil of 

 olives are displayed more strikingly. 



When one drop of oil of almonds is added to ten drops of oil 

 of cinnamon, and one drop of the adulterated oil is placed on 

 water, there is a shooting out of minute globules in radial lines, 

 which is characteristic of oil of cinnamon ; a delicate film is 

 formed with holes in the edge which close and open again, and 

 in a few minutes cohesion gathers up the film in the form of 



