j The influence of forests upon the dews is 

 important; and depends upon the greater hu- 

 midity and coolness imparted to the air around 

 them, and to the shelter from the winds which 

 they furnish. In the immediate shade of a 



. a tree, the radiation from the earth may be in 

 part returned, and less may be deposited; but 

 a little further off, the humid influence of a 

 ; grove is decidedly observed. To this may 

 perhaps be ascribed the freshness of pastures 

 interspersed with clumps of trees, at a time 

 when a naked pasture will be parched and 

 brown. § 



We should not forget to mention the rela- 

 tion existing between malaria and growing 

 trees. Fortunately in our State diseases occa- 

 sioned by malarious .exhalations have, in a- i 

 great degree, disappeared from the central 

 and western portions, since the decaying mould 

 : and rotten wood exposed to the air in the new 

 clearings have become thoroughly decom- 

 posed. But in warmer climates, where rank 

 j vegetation is allowed to decay in wet places, 

 this poisonous element acquires its greatest 

 virulence. Such are the Pontine Marshes near 

 the city of Rome, where an overflow from 

 obstructions in the Tiber, and neglect of 

 \ agriculture has brought on an insalubrity 

 ! throughout a once healthy and fertile region, 

 ! which ages of patient industry can scarcely 

 redeem. It has been found, that next after 

 the drainage of the spongy morass, which a 

 luxuriant and neglected growth of herbage 

 had occasioned, the planting of trees in belts 

 and groves, affords the best means of absorb- 

 ing the poison, and preventing its dispersion 

 by the winds. The cutting down of a forest, 

 which for ages had covered the slopes of a 

 hill between the city and the marshes, let in 

 the malaria upon a part of the city where it 

 was before unknown. 



The Eucalyptus, an Australian tree of most 

 vigorous growth iu warm countries, has been 

 of late especially noticed as capable of absorb- 

 ing the poisonous exhalations of marshes. A 

 recent writer || gives many instances of its suc- 

 cessful treatment of malaria-. It is asserted 

 tbat this tree will absorb from the earth ten i 

 times its weight of water daily, giving ofl { 



sin India dew is deposited near rivulets when 

 all around is perfectly dry. Tlie limit of deposi- 

 tion was but firtaeu or twenty feet. — [Col, Bykes, 

 In Transactions of Royal Soc, 185U, p, 35i. 



il Monthly Kepnrt Departraent of Agriculture, 

 December, 1Z7i. 



' with the renovated emanations of its foliage a 

 camphorated aroma, alike antiseptic and 

 agreeable. 



Somewhat similar properties are claimed for 

 ; the long-leaved pine and other trees, as well 

 as. for the sunflower, planted in belts along 

 the border of marshes. Wherever intermit- 

 tent fevers appear to be occasioned by 

 marshes, the planting of trees along the margin 

 of the wet lands, so as to break the winds 

 passing over them, would, in all probability, 

 be followed by a decided abatement, if not a 

 complete suppression of the evil. It is to be j 

 remembered that prevailing sickness from 

 malaria seldom appears in our climate so long 

 as the country is timbered, but only as decay- 

 ing ve.getable matter is exposed to the sun. 



It is quite probable that electrical conditions 

 dependent upon vegetation may have a de- 

 cided influence upon the precipitation of rain. 

 We know that a hispid plant, insulated and 

 heavily charged with electricity, quickly loses 

 < its charge, and that every point of a leaf or 

 plant is an agency for receiving or passing oft 

 an electrical current. The telegraph wire is 

 robbed of its message in passing through a 

 tree top, if contact with the foliage is allowed; 

 and I have no doubt but that a house sur- | 

 rounded by high trees is better guarded ! 

 against lightning than if protected by a patent 

 lightning rod of average construction, 

 j There is scarcely a change of condition or 

 ' of place in nature, in which electrical phe- | 

 nomena may not be noticed, when carefully 

 I observed. The passage of water into vapor, 

 its condensatioa into rain, the fi-iction of the 

 winds, a change from heat to cold, or from , 

 cold to heat, combustion and slow decay, are ' 

 all attended by electrical phenomena. In its . 

 ordinary conditions the air is positively elcc- 

 trifled, but in fogs, rain and snow, and some- 1 

 : times in cloudy weather it is negative. The 

 conditions change with the hours of the day 

 and the season of the year. The facility 

 with which electricity passes from points or 

 is received by them, suggests the probability 

 that forest vegetation must have a marked in- 

 fluence upon these conditions and changes. 



I should not omit to notice the benefit of 

 copses and belts of woodland scattered among 

 cultivated fields, for the shelter they afibrd to 

 I insectivorous birds. A very large proportion 



