164 Intelligence and Miscellaneous Articles, 



nights with my thermo-electric pile, and satisfied myself that this 

 instrument is eminently fitted to examine " the mixed action of our 

 atmosphere and stellar space," as regards radiation. My observa- 

 tions are referred to in the Philosophical Magazine, vol. xxii. p. 470. 

 I still preserve my little observatory on the roof of the Royal Institu- 

 tion, in the hope of being able to carry out the idea expressed in a 

 note at the page referred to. Until this has been done, any opinion 

 of mine on the questions raised by my distinguished correspondent 

 M. Buys Ballot, would be of little value ; but I am glad to see the 

 subject in such excellent hands. It also gives me pleasure to find 

 that M. Poey has recently turned the thermo-electric pile to account 

 in examining the atmosphere of Havana. This zealous observer 

 thinks that his observations regarding the action of aqueous vapour 

 are diametrically opposed to mine : I, however, entertain a strong 

 hope that M. Poey himself will eventually clear up the apparent dif- 

 ference. The experiments demonstrative of the action of aqueous 

 vapour on radiant heat of low refrangibility are, in my opinion, per- 

 fectly conclusive. — John Tyndall.] 



ON CALORESCENCE. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 

 While the changing of the ultra-red rays of the spectrum of the 

 electric light into a complete luminous spectrum agrees so far with 

 the phenomena of fluorescence, that in both cases the change of 

 period is wrought by the intermediation of ponderable substances 

 which alter the rate of oscillation, still the fact that the one class of 

 effects is produced in bodies at ordinary temperatures, while the 

 other class requires the temperature of incandescence for their pro- 

 duction, introduces a marked distinction between them. Instead, 

 therefore, of the two words " negative fluorescence " provisionally 

 adopted by me in an article in the January Number of the Philoso- 

 phical Magazine, I would propose the word Calorescence to express 

 the rendering of bodies luminous by the heat of the ultra-red rays. 



John Tyndall. 



A LETTER FROM JOHN DAVY, M.D., F.R.S., ADDRESSED TO THE 

 EDITORS OF THE PHILOSOPHICAL MAGAZINE, IN CONTINUA- 

 TION OF A FORMER ONE, AND ACCOMPANIED BY DOCUMENTARY 

 EVIDENCE CONTRIBUTED BY SIR JAMES SOUTH, F.R.S., AND 

 BENJAMIN GOMPERTZ, ESQ., F.R.S., IN REPLY TO A CERTAIN 

 CHARGE MADE BY CHARLES BABBAGE, ESQ., F.R.S., AGAINST 

 THE LATE SIR HUMPHRY DAVY WHEN PRESIDENT OF THE 

 ROYAL SOCIETY. 



Gentlemen, 

 Referring to my letter to you of the 20th October, published in 

 the Philosophical Magazine for December in reply to certain 



