1896.] on the Circulation of Organic Matter. 161 



same authority states that nitrification does not take place under 

 water, and careful experiments carried out at Tokio show that sulphate 

 of ammonia is a much better manure for irrigated rice than nitrate of 

 soda. 



In our damp climate sewage farming has proved a dismal failure, 

 and the difficulties seem to increase with the quantity of water which 

 has to be dealt with. Excess of water drowns the humus, and nitri- 

 fication cannot go on in a soil the pores of which are closed by excess 

 of moisture. 



The living earth, teeming with aerobic microbes, must be allowed 

 to breathe. It needs for this purpose a certain amount (about 30 per 

 cent.) of moisture, but it stands drowning no better than a man does, 

 and if it be drowned, agricultural failure is inevitable. 



If we carefully return to the upper layers of the humus, in which 

 air and microbes exist in plenty, the residue of everything which we 

 extract from it, we inevitably increase the thickness of the humus and 

 its fertility. Our capital increases, and our dividends increase and 

 recur with a frequency which depends upon the climate. 



With tlirifty and high cultivation it may, indeed, prove profitable 

 to compensate defects of climate by the use of glass and artificial 

 heat. 



The part played in the economy of nature by fungi and bacteria— 

 the new learning of the last half-century — is an addition to human 

 knowledge which is destined to revolutionise our views of many 

 natural phenomena. It has already exercised enormous propulsive 

 power on human thought, and has stimulated our imaginations scarcely 

 less than when, to use the words of Froude, " the firm earth itself, 

 unfixed from its foundations, was seen to be but a small atom in the 

 awful vastness of the universe." 



This knowledge has provided us with a new world peopled with 

 organisms in numbers which, like the distances of the astronomers 

 and the periods of the geologists, are really unthinkable by the 

 human mind. Their variety also, both in form and function, is, for 

 practical purposes, infinite. 



When, with the help of the many inventions of the optician and 

 the dyer, we catch a glimpse of things which a few years back were 

 "undreamt of in our philosophy," and when we reflect that these 

 organisms are certainly the offspring of " necessity," and are probably 

 mere indications of infinities beyond, we cannot be too thankful for 

 the flood of light which these discoveries have shed upon the enormity 

 of human ignorance. 



The lower animals and the lower vegetable organisms (fungi and 

 bacteria) co-operate in a remarkable way in the circulation of organic 

 matter. 



In the autumn the gardener, with a view to what is called '* leaf 

 mould," sweeps the dead leaves into a heap where they are exposed 

 to air and rain. This heap when thus treated gets hot, and last 



Vol. XV, (No. 90.) m 



