236 NATURAL HISTORY 
LETTER XXVIII. 
Selborne, Feb. 7, 1776. 
Dear Sir,—In heavy fogs, on elevated situa- 
tions especially, trees are perfect alembics ; and no 
one that has not attended to such matters can ima- 
gine how much water one tree will distil in a 
night’s time, by condensing the vapour, which trick. 
les down the twigs and boughs so as to make the 
ground below quite in a float. In Newton Lane, 
in October, 1775, on a misty day, a particular oak 
in leaf dropped so fast that the cartway stood in 
puddles and the ruts ran with water, though the 
ground in general was dusty. 
In some of our smaller islands in the West In- 
dies, if I mistake not, there are no springs or riy- 
ers; but the people are supplied with that neces. 
sary element, water, merely by the dripping of 
some large tall trees, which, standing in the bos 
of a mountain, keep their heads constantly envel- 
oped with fogs and clouds, from which they dis. 
pense their kindly, never-ceasing moisture, and so 
render those districts habitable by condensation 
alone. 
Trees in leaf have such a vast proportion more 
of surface than those that are naked, that, in the- 
ory, their condensations should greatly exceed those 
that are stripped of their leaves ; but as the former 
imbibe also a great quantity of moisture, it is diff. 
cult to say which drip most; but this I know, that 
deciduous trees that are entwined with much ivy 
seem to distil the greatest quantity. Ivy-leaves are 
smooth, and thick, and cold, and therefore con. 
dense very fast; and, besides, evergreens imbibe 
GI A I 
