Proceedings of the Polytechnic Association. 1027 



cannot be, and if malaria is present there is no ozone. They are 

 antagonistic, and mutually neutralize each other. 



Eunning water is a great agent fur purification. AVhen decaying 

 organic matter enters a running stream, the occluded oxygen in the 

 water immediately burns it up. The motion of the water brings 

 new portions of water to the surface to absorb more oxygen, and it 

 continues its action till all hurtful materials are consumed. The 

 ocean, by its constant motion, accomplishes the same thing. Hence 

 no malarious matter arises from a running stream or from the surface 

 of the ocean. 



Vegetation plays a most important part in purifying the air. As 

 all know the surface of leaves is pierced with innumerable mouths 

 (stomata) which drink in carbonic acid and give out oxygen. Malaria 

 cannot pass healthy, vigorous leaves. It either enters the leaf and 

 is decomposed with the carbonic acid, or tlie oxygen, in the state 

 eliminated, is in the form of ozone and consumes the malarious 

 matter. We have found malaria near the ground under a tree, and 

 ozone among its foliage. The effects of vegetation on malaria have 

 not been very long known, or if known, not acted upon ; some even 

 deny its beneficial effects now, but facts are too numerous to leave 

 any doubt on the subject. 



We are told that Rome and the plains of Latium were anciently 

 covered with woods, lakes and marslies, and Rome was healthy and 

 Latium was thickly settled. The woods were cut down and Latium 

 became a desert, and Rome was attacked with agues and remittent 

 fevers. In 1695 Rome was visited with much sickness, except one" 

 portion surrounded by a belt of trees, whicli escaped the infiictiou. 

 "We could multiply examples without number by the influence of 

 vegetation in arresting malaria. All swamps are not malarious. A 

 swamp growing the taxodium distichura (bald cypress), nyssa uniflora, 

 with the surrounding trees hung with the tillandsia usneoides (long 

 moss), is sure to be malarious. But if we find the cupressus thyoides 

 (wliite cedar) pinus serotina bordered with the pinus palustris and 

 tussocks of vigorous grapes, we shall find very little malaria. One' 

 accustomed to feel the effects of malaria can at once perceive its 

 presence by its influence. A peculiar sensation accompanied by 

 depression of vital powers and headache leaves no doubt of the' 

 presence of this marsh poison. We have often removed these 

 impressions by going to a non-malarious position and breathing with 

 deep and long inspirations for fifteen or twenty minutes. The 



