1816.] Prevost’s Theory of Radiant Heat. 303 
themselves lose heat equally by their own radiation, but receive 
equally their compensation. 
Now, fill this canister with a freezing mixture: and I will take 
the liberty to put to Dr. Murray two questions. ; : 
1, Has not the blackened surface lost a part of its intensity of 
radiation ? 
This cannot be denied : for the theory supposes bodies to radiate 
in proportion to their temperatures. 
2. Has the polished surface lost its power of reflection ? 
The answer must be in the negative, for the power of reflection 
does not vary with the temperature. 
It follows then that unequal diminutions have been imposed on, 
those powers of returning heat to the thermometer which before 
were equal. ‘The radiating surface has lost more than the reflecting 
surface, and its thermometer receives less return than that on the 
reflecting side. 
~_ If this should appear to Dr. Murray, (as I cannot refrain from 
saying it does to me) to be a demonstration, 1 am sure he is far 
above an unwillingness to acknowledge it assuch. If otherwise, I 
shall consider myself much obliged by his pointing out through the 
same channel such fallacy as he may detect in it. 
Iam, Sir, your very obedient servant, 
March 12, 1816, RicHarD Davenport, 
ARTICLE X. 
Proceedings of Philosophical Societies. 
ROYAL SOCIETY. 
On Thursday the 29th of February a paper by Mr. Ivory was 
read, containing an investigation of the theory of the attraction of 
capillary tubes. It has been long known that liquids rise in capil- 
lary tubes to heights which increase as the bore of the tube di- 
minishes. ‘This is universally ascribed to the attraction between- 
the atoms of the tube andthe fluid. Clairaut considered this attrac- 
tion as extending to a sensible distance. But Newton, Brook 
Taylor, Hauksbee, Laplace, &c. were of opinion, that it is eva- 
nescent at sensible distances, and of course extends only over an 
extremely small sphere. - Mr. Lesly, in a paper printed in the. 
Philosophical Magazine for 1802, considered the effect of an attrac- 
tion perpendicular to the surface of the fluid; and this also has 
been done by Laplace. As the thickness of the glass tube produces 
no effect upon the height to which the fluid rises in it, Mr. Ivory. 
considers the opinion of Newton as established. He conceives, 
likewise, that his mode of investigating the subject has some ad- 
Vaptages over that of Laplace; but as from the mathematical 
