2\)S 
ON CHEMISTRY. 
with different degrees of force—“in,the operation of this principle, 
conjoined with the power of a concave mirror o f clouds or any other 
awning, to reflect, or throw down again those calorific emanations 
which would be dissipated in a clear sky, we shall jind a solution of 
the most mysterious phenomenon of dew." 
In the last few lines with inverted commas the reader will find 
a condense of Dr. Well’s theory, and in the preceding part of the 
paragraph, that of other reasoners. 
It may he proper to remark that, in the same principle of radia¬ 
tion is to he traced the protecting power of a covering over fruit-trees 
in early spring. 
I agree with these authorities in as far as effects are discernable; 
but I seek a cause ,—an active agent—which cannot be discovered in 
their theories. I therefore retain the same opinion which I expres¬ 
sed some years ago, and must now shortly recur to it ; and thus, 
bring the long paper to a close. 
I do not question, or doubt, that radiation takes place from heated 
surfaces, whenever a cooler medium acts upon those surfaces; the 
ground, whether it be a sandy desert, or a meadow richly clad with 
verdure, will radiate heat; but how comes it to pass that the latter 
will become colder than the atmosphere which surrounds it P 
The radiation alluded to in the theory is supposed to be produced 
by vegetable organised bodies, and to result from a faculty which 
they possess of carrying off heat from the earth. But before the 
reader yields his unqualified assent to this begging of a question, he 
should reflect upon the peculiar structure of the radiators, and the 
wonderful electric agencies which are ever in active operation. Ve¬ 
getables, including herbage, shrubs, and trees,—every pointed ter¬ 
mination of their leaves, and their terratures, every leaflet, every 
prickle and bristle,—all these perform some important offices in the 
economy of nature: they are <c the best of radiators, and become 
soonest dewed”—but at the same time—be it remembered—they con¬ 
stitute an assemblage of so many points, which are the very best of 
electrical conductors; and, probably depend upon the agency of 
electricity for the propulsion, laboration and distribution of their own 
vital and secreted fluids. 
Why should trees and herbage condense such a vast volume of 
water P Why should a spot of freshly digged ground be covered with 
hoar-frosty when hard, unwrought ground discovers not one particle 
of lrostv rime, unless it be on spots where some weed or projecting 
point be standing above the surface P let those answer these ques¬ 
tions with calmness, and by philosophical reasoning, who j>ersist in 
