322 Intelligence and Miscellaneous Articles, 



towards the light," I might have also laid claim to the explanation, 

 as I happened to be engaged in a course of experiments to illustrate 

 the proposition he proved. My reason for alluding to the subject 

 now is that I may mention an hitherto undervalued fact which I 

 observed during their progress. 



I commenced my research with the idea that it might possibly 

 happen that Light would act as a sort of analyser, separating vola- 

 tile substances from each other. I fancied, for instance, if camphor 

 moved towards the light, other volatile matters might move in an 

 opposite direction, or that certain circumstances might determine 

 such a course. It would be useless to mention any of the substances 

 I experimented on, or the circumstances in which I placed them, as 

 I ultimately came to the conclusion that light was not the moving 

 power at all, but temperature. 



During these trials I dissolved, in a saturated solution of camphor 

 in alcohol, some iodine, so as to colour it darkly ; and having ex- 

 posed a little of this mixture in a corked flat phial in a window, I 

 found that on whichever side was the warmer the coloured fluid rose 

 by capillary attraction, and on that side only. With other coloured 

 fluids I observed the same action ; and I found, in fact, that I had a 

 most sensitive differential thermometer, for no matter how slight 

 the difference of temperature of the sides, although inappreciable to 

 the most delicate thermometer, the capillary attraction caused a rise 

 of the liquid on the side of the vessel which was nearer to the heat, 

 and the height attained seemed to be in proportion to the difference 

 of temperature. 



If vapour of -water be in the phial — a condition easily brought about 

 by placing a drop or two 6i this fluid on the side of the vessel 

 within, not mixing them with the spirit,— it will always be deposited 

 on the side opposite to that on which the rise of fluid by capillary 

 attraction takes place, no matter how the light falls on the bottle ; 

 showing, of course, that the cold surface condenses the vapour, and 

 the hot one causes the fluid to rise. 



And when we consider that the sides of the phial containing the 

 coloured fluid and enclosing the vapour are only about half an inch 

 apart, and that the vessel is placed where no difference of temperature 

 of its sides apparently exists, we are tempted to think that the 

 vapour is condensed more in the direction than in the actual presence 

 of the cold, while the coloured fluid is raised in the opposite — radia- 

 tion having more to do with the phenomena than sensible difference 

 of temperature. 



However this may be, the delicacy of this simple contrivance (a 

 flat corked phial, in which is contained a little coloured spirituous 

 liquid and vapour of water) for showing difference of temperature in 

 opposite points is remarkable, and might, I think, be taken advan- 

 tage of in meteorological investigations. 



When the fluid is raised, and the vapour deposited, if the vessel 

 is turned round so as to reverse the aspect of the sides, the fluid 

 entirely leaves the side now pointing to the colder region, and rises 



