360 Mr. C. Tomlinson on the Motion of Vapours 



one who has so eminently distinguished himself in original 

 investigation should have chosen to superadd to his functions as 

 a discoverer those of a severe and hostile critic upon the labours 

 of those men who have worked at the same subject with himself, 

 and by all of whom he has been treated with the utmost possible 

 consideration. 



I remain, 



My dear Sir David Brewster, 



Yours very truly, 

 5 Alva Street, Edinburgh, B. Stewart. 



April 10, 1863. 



L. On the Motion of Vapours toward the Cold. By Charles 

 Tomlinson, Lecturer onPhysical Science, King's College School, 

 London. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



I HAVE just been arranging for repetition Dr. Woods's in- 

 genious and beautiful experiment on the motion of vapours 

 toward the cold, as described by him in the current Number of 

 your Magazine. 



While engaged last summer in investigating the law of the 

 motions of camphor, &c. toward the light, I performed a number 

 of experiments in the same direction as that by Dr. Woods. 

 They were not described in my paper inserted in your Magazine 

 for November last, because in it, as at the British Association 

 Meeting in October, I wished to be as concise as possible ; but 

 you will remember that in my published paper I state (p. 361) 

 that " I omit many subsidiary facts observed during the inquiry." 

 The following are a few of them. 



On the 21st of May, 1862, a solution of iodine in bisulphide 

 of carbon was put into a stoppled eight-ounce phial in quantity 

 sufficient to form a ring at the bottom and to surround a central 

 convex island. The bottle was placed in a west window. The 

 day was cloudy and wet. In the course of an hour a violet dew 

 was formed a little above the solution. In another half hour 

 (i. e. at noon) the dew became more copious, and extended over 

 nearly the whole surface of the bottle, but was densest on the 

 side nearest the light. In another half hour (12.30 p.m.) the 

 beads of dew were smaller and paler. At 1 p.m. they had 

 become almost colourless, and solid iodine had condensed on the 

 convex island at the bottom of the phial. At 3 and also at 

 4 p.m. there was a gleam of sunshine, when the bottle became 

 filled with a yellowish vapour and the dew again became coloured, 



