FROM DUST TO DUST. 53 



obtain it by means of nitrifying bacteria. Darwin has shown that 

 Drosera, Dioncsa muscipiila^ Utricular ia^ and other insectivorous 

 plants obtain their nitrogen from insects, larvae, and other small 

 organisms, which are caught in their traps. 



Schloesing and Miintz, in 1877, demonstrated that a living 

 ferment was necessary for the production of nitric acid and nitrates 

 in the soil ; but it was due to the researches of Prof Percy Frank- 

 land and Mrs. Frankland, Warington, and Winogradsky, that the 

 complete knowledge of the process of nitrification was obtained, 

 and that two different bacteria were necessary to accomplish it, 

 one of which converts ammonia into nitrous acid, when the other 

 takes up the work and produces nitric acid in a form which can be 

 assimilated by plants. These have now been completely isolated, 

 and it is remarkable that the nitric-acid-forming bacterium was first 

 found in a sample of soil taken from a region near the great salt- 

 petre layers of Chili. European soils contain much smaller 

 quantities of nitrates than those of South America or Africa, but 

 this has been accounted for by the much greater rainfall in Europe, 

 which removes the soluble salts from the surface of the soil, whilst 

 the dryness of the tropical climates of Chili and Peru allows them 

 to accumulate. It is quite conceivable that the rapid growth of 

 vegetation which occurs in an Arctic or Alpine summer, may be 

 due to the accumulation of nitrates in the soil, which has been 

 kept dry and comparatively warm by the snow for so many 

 months. / 



We all know what an immense benefit the importation of 

 nitrates has been to agriculture, and also that manufactured 

 nitrates have been of some use. It remained, however, for 

 Science to show that, besides importing the nitrates, we also 

 imported the nitrifying organisms, which continue to fertilise our 

 lands (even after the nitrates themselves have been used up) by 

 acting upon the ammonia in the manures, which we afterwards 

 supply to them. Hitherto our methods of cultivation have been 

 empirical, and one of the great maxims has been " to expose the 

 soil to the air.'' Empiricism, the result of well-observed experi- 

 ence, has nearly always proved right knowledge. Science explains 

 the knowledge obtained by empiricism, develops it, and by deduc- 

 ing general laws and principles gives it wider scope of action. 



