Camphor towards the Light. 361 



city from a few ounces to a quart and more. These were charged 

 with various quantities of crude camphor, from 2 or 3 grains to 

 100, and were placed in the window on flat supports at the 

 junction of the sash-bars, and also in various other positions 

 with respect to the light as occasion required. An arrow point- 

 ing to the light was marked on every bottle, and in many cases 

 the date when the bottle was first exposed. 



It may here be stated once for all, that the substances which 

 produce good deposits are ordinary refined camphor, Borneo 

 camphor, oil of camphor, artificial turpentine camphor, chloral, 

 naphthaline, iodine, mercury, sesquichloride of carbon, water, 

 alcohol, &c. 



I must confess that in the early part of the inquiry the whole 

 subject of these camphor motions seemed to be beset with diffi- 

 culties. I not only obtained Dr. Draper's results, but others 

 equally surprising and contradictory so long as the action of 

 light was looked for. I did not presume to suppose that 

 ChaptaPs statement, indorsed as it was by the honoured name of 

 the late Professor Daniell, and by the names of all chemists of 

 repute, was altogether a mistake ; but when I considered some- 

 what the history of science, and remembered that Chaptal wrote 

 at a time when men had no correct views on many parts of the 

 science to which I was led to refer these phenomena — when, for 

 example, the present theories of radiant heat and of dew, of 

 evaporation and condensation did not exist, — I was led to think 

 that my presumption might be pardoned if I ventured to pro- 

 pound an entirely new theory as to the motions of camphor, &c. 

 towards the light. 



As my object is to make a short statement, I omit a number 

 of details which led me to adopt a new theory. I also omit 

 many subsidiary facts observed during the inquiry. What led 

 me to suspect that light had nothing to do with the camphor 

 deposits, was the fact that during about a week of fine weather 

 early in May the bottles in the east windows showed deposits 

 furthest from the light, while those in the west windows were 

 nearest to the light. In order to test this result more closely, 

 four quart stoppled bottles, A, B, C, D, were supplied each with 

 100 grains of crude camphor in coarse powder and placed as 

 follows : — A in the west window, B outside the west window on 

 the balcony, C in the east window, and D outside the east win- 

 dow. The outside bottles were tied over with india-rubber cloth. 

 In the course of the day deposits were obtained in all four bottles, 

 varying in position and character, clearly establishing the fact 

 that, while one of the indoor bottles was forming a deposit 

 furthest from the light, the corresponding outside bottle had its 

 deposit nearest to the light. The two bottles, within a few feet 



Phil Mag. S. 4. Vol. 24. No. 163. Nov. 1862. 2 B 



