298 NATURAL HISTORY 



LETTER XXIX. 



TO THE SAME. 

 DEAR SIR, SELBORNE, Feb. 7, 1776. 



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 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 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 entwined with much ivy seem to distil the greatest 

 quantity. Ivy leaves are smooth, and thick, and cold, 

 and therefore condense very fast ; and besides, ever- 

 greens 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 



