45 



various circumstances, but two conditions are remarkable, one 

 where the agents are animals, and the other where the agents 

 are chemical. Animal life may act in various amounts on 

 vegetation in the soil, from the large vermin to the microscopic 

 classes. These do not prevent chemical action, on the con- 

 trary, it is probable that they further it exceedingly. 

 Decomposition goes on in the soil at various rates, and in 

 various ways. In a rich, highly-manured soil kept warm, 

 the soil will be found alkaline. Soils generally are acid. 

 The Author had shown in a Paper, read in 1847, that in an 

 alkaline, peaty district, cold weather produced acidity in a few 

 days. It would appear as if the acids of the mould (so 

 elaborately described by Mulder) were incapable of further 

 decomposition in the cold, and were thus retained and 

 increased. Our great struggle with the soil is to produce 

 alkalinity, or at least to diminish acidity, and where most 

 acids exist we use most lime. Where most alkali exists there 

 is a greater facility for the escape of vapours, such as we 

 suppose to be hurtful. So far as the vapours of putrid 

 substances have been examined by the Author, they have 

 shown indications of containing substances composed some- 

 what like protein, at least the carbon and nitrogen have had 

 relations to each other similar, or nearly identical with those 

 found in protein, and formed the mass of the substance. 



The extreme condition of putrescence may be very readily 

 produced in a soil by artificial means ; the use of a little 

 ammonia, for example, more than vegetation will bear. The 

 substances putrefy until the whole becomes foetid in the 

 highest degree. We have then a soil rich in organic matter 

 and undrained. It is a swamp of the worst form if the soil be 

 not very poor ; worse, perhaps, than was ever seen in nature. 

 Such a soil would bring death everywhere. It is artificial 

 malaria. We can, then, produce malaria from the soil by 

 fostering some of its tendencies ; and we see by the rapid 

 acidification of soil, in colder weather, why malaria is 

 diminished by a lower temperature. 



