280 TREES FOR SHADE AND SALUBRITY. 



laws of these influences ; and as the chloride of lime 

 disinfects the foul air of a chamber, it may appear that 

 there are emanations from the leaves of trees, combined 

 with their absorbent action, that purify the atmosphere 

 in more ways than have yet been imagined. These hints 

 are only conjectures; but the fact is admitted by the 

 pioneers of the Western States, that the man who culti- 

 vates a small clearing in the forest is secure, while the in- 

 habitant of the prairie or of a clearing that occupies the 

 space of several miles is subject to fever and ague and 

 other malarious fevers. 



The greater warmth of a wood in summer after dew- 

 fall and during all the early part of the night, when 

 people are generally out of doors, contributes very greatly 

 to the salubrity of a forest. The malaria are most perni- 

 cious to those who are exposed to the damp chill and 

 dews ; and it is well known that those who keep within 

 doors after dewfall in summer are generally exempt from 

 fevers. The temperature of the atmosphere within a. 

 wood being warmer than the outer air, whenever the dews 

 are falling, as in the early part of all still summer nights 

 in clear weather, the dwellers in the wood are pro- 

 tected from chills to which the inhabitants of the open 

 districts are exposed in the evening of almost every day. 

 Probably it is a combination of all these circumstances 

 that causes the general salubrity of a residence in a wood ; 

 and an increased knowledge of the facts that bear upon 

 this subject would probably multiply our motives for the 

 preservation of the forests. 



All these remarks apply chiefly to assemblages of wood 

 of considerable extent. When a few trees surround a 

 house standing on an open plain, they do not produce all 

 the effects we experience in a wood. They are not suffi- 

 cient to enclose within their area an atmosphere that is 

 not immediately affected by the temperature and moisture 



