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. 
