196 DRIPPING OF TREES. 



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 wish to be 

 perennial ; and shew 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 



made, almost as deep as the pith, under some well spreading branch, 

 into which a small stone or chip is inserted to keep the lips of the wound 

 open. To this orifice a bottle is attached to collect the flowing juice, 

 which is limpid, watery, and sweetish, but retains something of both 

 the taste and odour of the tree. One tree affords two or three gallons 

 a day ; at the same time, it receives no perceptible injury from being 

 thus bled, from which it would appear, that much of its moisture 

 has at other times been given off through its leaves ; and, in all proba- 

 bility, it acquires an increased action to supply the extra quantity which 

 is thus drained from it. ED. 



* There can be little doubt, that the moisture of climate is greatly 

 influenced by trees. It has been remarked, after cutting down forests, 

 particularly on high grounds, that the quantity of rain has been lessened, 

 by diminishing, it is supposed, the attraction between the earth and the 

 clouds. This fact has been experienced on a large scale in America. 

 In Kentucky there are many brooks, now completely dry in summer, 

 which afforded an abundant supply of water all the year round about 

 twenty-five or thirty years ago ; and, in some parts of the state of New 

 Jersey, where the woods have been extensively cleared away, many streams 

 have altogether disappeared. 



The climate of Britain, it is very generally believed, has deteriorated by 

 becoming much more changeable than it was sixty years ago. This has, 

 with much probability, been attributed to the extent of planting, to the 

 introduction of green crops, and abolition of fallows in an improved sys- 

 tem of agriculture. Mr Murray is of opinion, that trees, by condensing 

 the moisture of the air in foggy weather, materially affect the climate, and 

 that thickly wooded countries must necessarily be colder, and more 

 humid than naked savannahs. Trees are, therefore, it would seem, ready- 

 conductors of aerial electricity, the climate being improved when woods 

 are cleared away, and becoming more moist by planting. This fact 

 receives corroboration from the history of our own country, as well as 

 from that of North America. ED. 



