2 o8 NATURAL HISTORY OF SELBORNE. 



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 

 la^ge teak 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, 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 evapora- 

 tion 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 

 forests have been grubbed and cleared, all bodies of water are 

 much diminished ; so that some streams, that were very consider- 

 able a century ago, will not 'now drive a common mill. Besides, 

 most woodlands, forests, and chases, with us abound with pools 

 and morasses ; no doubt for the reason given above. 



To a thinking mind few phenomena are more strange than the 

 state of little ponds on the summits of chalk-hills, many of which 

 are never dry in the most trying droughts of summer. On chalk- 

 hills I say, because in many rocky and gravelly soils springs usually 



