Hence there is reason to think that, contrary to the general opinion.
white garments are warmer than any other in cold weather; and in-
deed if they are well calculated to reflect calorific rays in summer,
they ought to be equally well calculated to reflect those frigorilic rays
by which we are annoyed in winter. Fur garments have been found
by experience to be much warmer in cold weather, when worn with
the hair outwards, than when it is turned inwards.
This is alleged as a proof that we are kept warm by our clothing not so much by confining the heat of our bodies, as by repelling those frigorific rays which tend -to cool us. The fur of several delicate animals we know becomes white in winter in cold countries; and bears which inhabit the polar regions are likewise known to be white in all seasons. Now if, in fact, as there is great reason to believe, white is the colour most favourable to the reflection of calorific and frigorific rays, it must be acknowledged that these animals have been greatly favoured in having a. clothing assigned them so well adapted to their local circumstances.
The excessive cold which is known to prevail, in all seasons, on the tops of high mountains, and the frosts at night which frequently take place on.the surface of the plains below, seem to indicate that frigariflc rays arrive continually at the surface of the earth from every part of the heavens; and it is no doubt by the action of these rays that our planet is continually cooled, and enabled to preserve the same mean temperature for ages, notwithstanding the immense quan- tities of heat that are generated at its surface by the continual action of the solar rays. The action of these frigorific nocturnal rays will likewise justify the inhabitants of hot climates, who, in order to be more cool during their hours of rest, remove their beds in summer to the tops of their houses.
a Letter from Thomas Andrew Knight, Esq. to the Right Hon. Sir Joseph Banks, Bart. K.B. P.R.S. Read February 16, 1804.
[Phi]. Trans. 1804, p. 183.]Some experiments are here described, the tendency of which is to prove, what the author had advanced as a conjecture in a former communication, that the vessels of the bark which pass from the leaves to the roots, are in their organization better calculated to carry the fluids they contain towards the roots than in the opposite direction.
In the first of these experiments several strong horizontal shoots of vines were depressed about their middle; and at that part, buried in the mould, contained in pots about ten inches in diameter: after some months of vegetation, when the shoots had nearly filled the pots with roots, they were separated from the parent stock, having at each side above the earth a certain length of the layer, with at least one bud upon each. The end towards the stock was called the inverted, and the other the proper end of the layer. If the author's
