OCTOBBB 28, 1898.] 



SCIENCE. 



671 



tainty and difiBculties. The land soon be- 

 comes what is called ' clover sick ' and 

 turns barren. 



There is still another and invaluable 

 source of fixed nitrogen. I mean the treas- 

 ure locked up in the sewage and drainage 

 of our towns. Individually the amount so 

 lost is trifling, but multiply the loss by the 

 number of inhabitants, and we have the 

 startling fact that, in the United Kingdom, 

 we are content to hurry down our drains 

 and water courses, into the sea, fixed nitro- 

 gen to the value of no less than 16,000,000L 

 per annum. This unspeakable waste con- 

 tinues, and no eifective and universal 

 method is yet contrived of converting sew- 

 age into corn. Of this barbaric waste of 

 manurial constituents Liebig, nearly half a 

 century ago, wrote in these prophetic 

 words : " Nothing will more certainly con- 

 summate the ruin of England than a 

 scarcity of fertilizers — it means a scarcity 

 of food. It is impossible that such a sinful 

 violation of the divine laws of Nature 

 should forever remain unpunished ; and 

 the time will probably come for England 

 sooner than for any other country when, 

 with all her wealth in gold, iron and coal, 

 she will be unable to buy one-thousandth 

 part of the food which she has, during 

 hundreds of years, thrown recklessly 

 away." 



The more widely this wasteful system is 

 extended, recklessly returning to the sea 

 what we have taken from the land, the more 

 surely and quickly will the finite stocks of 

 nitrogen locked up in the soils of the world 

 become exhausted. Let us remember that 

 the plant creates nothing ; there is nothing 

 in bread which is not absorbed from the 

 soil, and, unless the abstracted nitrogen is 

 returned to the soil, its fertility must ulti- 

 mately be exhausted. When we apply to 

 the land nitrate of soda, sulphate of am- 

 monia or guano we are drawing on the 

 earth's capital, and our drafts will not per- 



petually be honored. Already we see that 

 a virgin soil cropped for several years loses 

 its productive powers, and without artificial 

 aid becomes infertile. Thus the strain to 

 meet demands is increasingly great. Witness 

 the yield of forty bushels of wheat per acre 

 under favorable conditions, dwindling 

 through exhaustion of soil to less than 

 seven bushels of poor grain, and the ur- 

 gency of husbanding the limited store of 

 fixed nitrogen becomes apparent. The store 

 of nitrogen in the atmosphere is practically 

 unlimited, but it is fixed and rendered as- 

 similable by plants only by cosmic processes 

 of extreme slowness. The nitrogen which, 

 with a light heart, we liberate in a battleship 

 broadside has taken millions of minute or- 

 ganisms patiently working for centuries to 

 win from the atmosphere. 



The only available compound containing 

 sufficient fixed nitrogen to be used on a 

 world-wide scale as a nitrogenous manure 

 is nitrate of soda, or Chili saltpetre. This 

 substance occurs native over a narrow band 

 of the plain of Tamarugal, in the northern 

 provinces of Chili, between the Andes and 

 the coast hills. In this raialess district, for 

 countless ages, the continuous fixation of at- 

 mospheric nitrogen by the soil, its conver- 

 sion into nitrate by the slow transformation 

 of billions of nitrifying organisms, its combi- 

 nation with soda, and the crystallization of 

 the nitrate, have been steadily proceeding, 

 until the nitrate fields of Chili have become 

 of vast commercial importance, and promise 

 to be of inestimably greater value in the fu- 

 ture. The growing exports of nitrate from 

 Chili at present amount to about 1,200,000 

 tons. 



The present acreage devoted to the 

 world's growth of wheat is about 163,000, 

 000 acres. At the average of 12.7 bushels 

 per acre this gives 2,070,000,000 bushels. 

 But thirty years hence the demand will be 

 3,260,000,000 bushels, and there will be 

 difficulty in finding the necessary acreage 



