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XLII. On the supposed Evolution of Heat from Vegetables. 
Leskeard, March 19, 1814. 
Sims, —Lw your Magazine for February, Mr. Forster in a note 
on January 30th, in his meteerological journal, attributes the 
thawing of the snow around trees and shrubs to the ‘ heat trans- 
mitted from vegetable bodies.”” Having observed the same ap- 
pearance, I at first also attributed it to the same cause; but 
from further observations I soon found reason to reject such an 
explanation of the phenomenon, because the snow, which lies 
around any substance whateyer is affected in a similar way. 
Stones and rocks, and large or small pieces of wood inserted in 
or lying on the ground amidst snow, present the same appear- 
ance precisely, as trees, shrubs, or any other living vegetables. 
Since then we cannot attribute the disappearance of the snow 
in the latter instance to heat, it strikes me that it may be ac- 
counted for in another way. During the late snowy season, I ob- 
served that the thaw uniformly commenced and proceeded only 
on the surfaces of the snow ; even that next the earth being con- 
siderably affected. The surface adjacent to a rock or other in- 
animate substance thawed slowly for a short time, till a free 
passage for the air was formed; afterwards melting as rapidly 
as the upper surface, and receding gradually from the rock as a 
centre. 
Thus, whatever the substance may be around which the snow 
has fallen,—when a thaw commences, all the surfaces of the snow 
absorb caloric in the same proportion, or nearly so; and conse- 
quently an uniform retreat of the whole depth of snow will take 
place, and a bare piece of ground will be seen around the sub- 
stance, of whatever kind it may be, in the form of a rude circle. 
I have not made the above observations as an argument 
against the supposition that vegetables give out heat, but merely 
to show that Mr. Forster’s explanation of the phenomenon which 
has occurred to both of us, does not in all instances hold good. 
This he will have an opportunity of observing, in all probability, 
during the next winter. It would be interesting to try a few 
experiments in order to elucidate this matter ; and also to deter- 
mine, by the thermometer, if possible, whether or not heat is 
reallyevolved during the circulation of the vegetable fluids. Is 
there any sensible heat in cold-blooded animals? If not, it 
seems improbable that vegetables should afford any. 
Yours, &c. 
CoRNUBIENSIS. 
To the Editors of the Phil. Mag. 
XLIII. Process 
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