METEOROLOGY. 
J 94 
with lamp-black. Directly over each of these, and supported by four 
sticks about two feet above the top of the box, I placed over the tin 
box a piece of tin, and over the wpoden one a piece of wood, coated 
with lamp-black, so that a space should be left between the top of the 
box and the suspended covering, through which heat might unobstruct- 
edly radiate. On a clear evening I placed the boxes in the most open 
part of my garden, a few feet distant from each other, and suspended a 
piece of wool in each by a silken thread fastened to a stick, going 
across the top of the box, and so that the wool should hang in the 
centre of each box, and about three inches below the top : the weight 
of the wool was the same in both boxes, being exactly one hundred 
grains. 
On examining the wool the next morning, I found that the weight 
of that which had hung in the tin box was increased to one hun¬ 
dred and forty-six grains, and felt quite wet, while that in the wooden 
box only weighed one hundred and twenty-one grains, and was scarcely 
damp. Now, to what can the deposition of moisture be attributed ? 
Undoubtedly it is owing to the surface of the wool becoming colder 
than the surrounding air ; but how, then, are we to account for this ? It 
could not possibly be caused by any electro-conducting property of the 
wool, as it was perfectly insulated by the silken thread; and being 
itself a non-conductor, it could not have afforded a passage to an 
electric current; besides which, how could G. J. T. explain, by his 
theory, the difference in the quantities of moisture deposited in the two 
boxes? But, accounting for it on the principle of the radiation of 
heat, we have not only an explanation why the wool should become 
colder than the surrounding atmosphere, but also a sufficient reason 
for the difference in the quantity of moisture deposited; for, as the 
greater part of the heat radiated by the wool in the wooden box, was 
radiated back again by the surface of lamp-black, its temperature did 
not fall so low as that in the tin box, which was surrounded by a 
polished surface, capable of returning but a very small portion of the 
heat given off. I know not if the details I have given of the experi¬ 
ment are sufficiently clear to render it intelligible, but I hope, in a 
future Number, to enter more at large on the laws relating to heat, 
and particularly in their connection with horticulture. 
Gosport, March 4th. 
J. B., Jun. 
