516 Agricultural Journal of Victoria. 



soda, already referred to as the basis of so many explosives. This 

 salt occurs naturally in certain regions of Chili and Peru, where for 

 countless centuries the continuous fixation of atmospheric nitrogen 

 has been carried on by bacteria. Unfortunately, however, like any 

 other mineral supply in the earth, the (juantity is limited, and although 

 it is difficult to get accurate estimates f)f the amount of nitrate re- 

 maining in the beds, authorities seem to agree that at the present 

 rate of export the raw material will all be exhausted within from 

 forty to fifty years. To show how much more rapidly this supply is 

 being exhausted than was thought possible forty years ago, it is only 

 necessary to state that in 18(30 all estimates showed that the amount 

 of nitrate of soda then known would last for nearly fifteen hundred 

 years. The demand has rapidly increased, however, and although 

 the output is controlled, there is annually consumed in the world's 

 markets nearly 1^ million tons of nitrate of soda, representing a value 

 of about !$100,000,000. Of this amount, the United States requires 

 about 15 per cent., and it is by far the most expensive fertilizer that 

 is in use by the farmer. 



In addition to the nitrate of soda beds there have also been large 

 deposits of guano, which have served as one of the principal sources 

 of nitrogen. The greater part of the guano beds are now completely 

 exhausted, however, and although new deposits are occasionally dis- 

 covered, they are of such limited area, or of such a low percentage of 

 nitrogen, as to have practically no effect upon the available nitrate 

 supply. 



There are certain other chemical salts which furnish a limited 

 amount of nitrogen, such as the product which remains from the 

 distillation of coal in the process of gas making, but all of them are 

 obtained in such comparatively small quantities that they are not 

 worth taking into consideration when one realizes the enormous 

 amount of nitrogenous fertilizer necessary to replace the combined 

 nitrogen which is annually removed from the soil in one way or 

 another. 



Ever since the importance of increasing the combined nitrogen 

 sup})ly has been realized, men of science have naturally turned to the 

 atmosphere as being the most promising field for experiment and the 

 one most likely to eventually solve the whole problem. When it is 

 remembered that nearly eight- tenths of the air about us is nitrogen, 

 and that plants are able to obtain their entire source of carbon from a 

 gas which is present in the comparatively small proportion of one- 

 tenth of one per cent., it seems almost incredible that there should be 

 any more difficulty about a plant's nitrogenous food than about its 

 supply of carbon dioxid. Since it seemed so well settled, however, 

 that plants could not use nitrogen as a gas, the chemists and 

 physicists have made every effort to devise some mechanical means 

 of making this element available in a combined form. It has been 

 known that discharges of lightning passing through the air are able 

 to fix free nitrogen, and, beginning with this as a basis, some very 

 satisfactory results have been obtained by the use of electricity. 



