INFLUENCE OF FOKESTS ON CLIMATE. 13 



were more frequent and abundant, the soil was shaded 

 and covered with leaves and other vegetable matter, 

 that prevented the rapid evaporation of moisture — a 

 portion of which must necessarily have found its way by 

 percolation into the ponds. The water in these ponds 

 was not only frequently renewed by showers, but pu- 

 rified by almost constant aeration, in consequence of the 

 visits of water fowls that frequented them in search of 

 food. Every ripple of the surface forced air beneath it, 

 and the movements of the birds — reptiles, amphibia, and 

 aquatic insects making their homes, or occasionally 

 visiting these ponds, assisted in aerating and purifying 

 the water. Ponds under such conditions never give off 

 fever germs, no matter in what country or climate they 

 may be located, but when they dry in consequence of 

 scarcity of rain, or the water is i-emoved artificially, 

 there is always more or less danger of the emission and 

 dispersion of fever germs. 



The draining of swamps, ponds — the changing of the 

 beds of streams — opening of new streets, even in our 

 older cities, as well as the breaking up of the virgin 

 soils of woodlands or prairies, are operations very likely 

 to be followed with outbreaks of chills and fever, among 

 the inhabitants of the neighborhood. The principles 

 that appear to govern the developemeut of fever germs, 

 are the same the world over, and if ponds, swamps, or 

 low lands are to be drained at all, it should be thoroughly 

 done, that there shall be no repetition of the danger 

 which usually follows the first disappearence of the 

 water therefrom. 



We naturally look to the old world for information 

 in i-egard to the influence of forests on climate, because 

 there men have paid the most attention to the subject, 

 at least in modern times, and even if we go further back 

 and grope about among ancient cities buried in drifting 

 sands, or pass over desert wastes, where once forests 



