NATURAL HISTORY OF SELBORNE. 199 
| A Wa SP ce cone Se 
TO THE SAME, 
SELBORNE, Fed. 7th, 1776. 
DEAR SIR,—In heavy fogs, on elevated situations especially, 
trees are perfect alembics ; and no one that has not attended to such 
matters can imagine how much water one tree will distil in a night’s 
time, by condensing the vapour, which trickles 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 cart-way 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 Indies, if I mistake 
not, there are no springs or rivers ; but the people are supplied with 
that necessary element, water, merely by the dripping of some large, 
tall trees, which, standing in the bosom of a mountain, keep their 
heads constantly enveloped with fogs and clouds, from which they 
dispense 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 theory, 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 difficult to say 
which drip most ; but this I know, that deciduous trees that are en- 
twined with much ivy seem to distil the greatest quantity. Ivy- 
leaves are smooth, and thick, and cold, and therefore condense very 
fast ; and besides, evergreens imbibe very little. These facts may 
furnish the intelligent with hints concerning what sorts of trees they 
should plant round small ponds that they would wish to be perennial ; 
and show them how advantageous some trees are in preference to 
others. 
Trees perspire profusely, condense largely, and check evaporation 
so much, that woods are always moist ; no wonder, therefore, that 
they contribute much to pools and streams. 
That trees are great promoters of lakes and rivers appears from 
a well-known fact in North America: for, since the woods and 
