46 



As we can imitate malaria of some kinds, so can we also 

 imitate the methods by which nature prevents it. The warm 

 alkaline soil, moistened, and washed with air and water, 

 becomes acid, it sends forth less volatile matter — decom- 

 position is stopped to a great extent, the matter is preserved. 

 Cold prevents the action, drainage assists oxidation by a more 

 active state of soil. By these modes, and others, the soil is 

 disinfected by nature, when these do not act sufficiently we 

 may use disinfecting agents. By their means decomposition 

 may be interrupted without fear of diminishing the power of 

 the plant to take up food. By the use of disinfecting agents, 

 Mr. Mc. Dougall had been able to feed sheep and cattle, and 

 retain them in health, on meadows constantly wet by irrigation 

 with liquid manure. The disinfectant used is from the pro- 

 ducts of the distillation of tar, the amount required is small. 

 Animal life is rapidly destroyed by it, and chemical decomposi- 

 tion is staid. All climates can furnish this, where coal lies or 

 where trees grow. 



It would be possible to irrigate great districts at an extremely 

 small expense. The result would be as certain on a large 

 scale as on a small one ; and it is probable that, in some cases, 

 one or two applications would be sufficient, for a long period at 

 least. By the new state of things, destructive insects would 

 also be destroyed. Although, according to Dr. Mc. CuUoch, 

 there are many parts of our own islands infected by malaria, 

 most, if not all, can be cured by good attention to well- 

 known agricultural maxims. This new method is especially 

 applicable to other countries, and to more violent stages of 

 the disease. The Author hopes to have it tried on extensive 

 districts in Italy. The method arose out of an advice every- 

 where neglected, but still cherished as true, to disinfect 

 whole cities by beginning with the sewers, the origin and 

 reservoir of all the mischief. 



The Author believes that he has shewn that decomposition, 

 to a most pernicious extent, is possible in soils, that this is 

 not a mere opinion, but a fact readily demonstrated ; but that 



