4a 



Public Parks. 



neutralizing propei'ty of their emanation, and remove from the air 

 the vapors by which it is contaminated."* 



M. Carriere, in a work on the climate of Italy, adopts the views 

 of Chevreul and Fontana, in relation to the febrific poison through 

 means of the action of organic matter on the sulphates contained in 

 the earth, or in water with the aid of the oxygen derived from the 

 former. The leaves of plants and of trees, as well as the green 

 substances that cover the soil, are all inexhaustible sources of 

 oxygen, which is so important to sustain life and preserve health. 

 "Hence," he says, "to cover the fields, the edges of marshes and 

 the whole extent of the soil with an abundant vegetation, is equal to 

 placing on the surface of unhealthy regions a reparative apparatus 

 of the greatest power. Trees, therefore, must have a large share 

 in the amelioration of the country, in consequence of the quantity 

 of leaves they furnish." t 



Others have supposed, before vegetable physiology was as well 

 understood as at this time, that malaria was collected by plants, 

 particularly those of a dense and entangling foliage, and was 

 disengaged in cutting them down or rooting them up, thus exciting 

 fevers and disease. Dr. Ferguson, calling attention to the atti"action 

 of marsh poison for, or rather its adherence to, lofty umbrageous trees, 

 says that "this is so much the case that it can with difficulty be 

 separated from them ; and that in the territory of Guiana particu- 

 larly, where these trees abound, it is wonderful to see how near to 

 leeward of the most pestiferous marshes the settlers, provided they 

 have this security, will venture — and that with comparative impu- 

 nity — to place their habitations. The town of New Amsterdam, 

 Berbice, situated within musket shot to leeward of a swamp 

 extremely offensive at a certain stage of dryness, owes evidently 

 its exemption from fever to this cause." " A still better instance of 

 the same, and with the same results, may be seen at Paramaribo, 

 the capital of Surinam, when the trade-wind, that regularly venti- 

 lates the town and renders it habitable, blows over a swamp within 

 a mile of the town, which, fortunately for the inhabitants, is covered 

 with the same description of trees." \ 



"It has been obsei-ved," says Becqueral, "that humid air, 

 charged with miasmata, is deprived of them in passing through 



* Journal de Physique. 

 t Le Climat de V Italie. 

 % Marsh Poison. 



