410 



Aofes on ilte Injlacncc 



[No. 36, 



In acklilion to the moisture which trees bring to the earth in the 

 form of rain they furnish a valuable supply by condensini,^ the fogs 

 Avhich occur. In heavy fogs, in elevuted situations especially, trees 

 are perfect alembics, and no one, who has not attended to such mat- 

 ters, 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. 



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 peren- 

 nial ; and show them how advantageous some trees are in preference 

 to others. 



Trees perspire profusely, condense largely, and check evaporation 

 so much that the woods are always moist, no wonder, therefore, that 

 they contribute much to pools and streams. In Newton Lane in 

 October on a misty day, an 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. 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 considerable 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. 



Trees require a great quantity of water to supply their organs. 

 This is given of! in perspiration by their leaves. In the experiments 

 of Hales, of the quantity of water taken up by plants, it was found 

 that a pear tree which weighed seventy-one pounds, absorbed fifteen 

 pounds of water in six hours and that branches of an inch diameter, 

 and from five to six feet high, sucked up from fifteen to thirty ounces 

 in twelve hours. When these were stript of their leaves, they only 

 sucked up one ounce in twelve hours. 



