346 THE POPULAR SCIENCE MONTHLY. 



facturiug countries. At Glasgow the works devoted to the produc- 

 tion of ordinary saltpetre from the nitre of Peru extend over acres of 

 ground. In 1868, 100,000,000 pounds were used in Great Britain. 

 As yet, it has been ajjplied to the nourishment of crops only to a 

 limited extent. But this seems to be its chief destination, and for 

 this use it lies in tlie earth, a vast mine of wealth, for the disposal of 

 coming generations. When multiplied population puts the sustaining- 

 power of the earth really to the test, this fund of sustenance on the 

 Peruvian coast must come to outweigh in value the gold and silver 

 mines of the Californian coast. 



Of the several nitrogen compounds which nourish plants, ammonia 

 yields the most immediately satisfactory results. And, of this fertil- 

 izing material, some wellnigh mineralized deposits must be counted 

 in with the earth's possessions. To take note of these ammoniacal 

 materials, we have again to begin at Peru. Standing on the shores 

 which front the nitre-beds, and looking westward upon the Pacific, 

 there are seen, as we are told, the low patches of the Cincha Islands 

 islands which shine with the whiteness of a powdery covering, a 

 loose deposit of considerable dejith. A cargo of this substance was 

 first taken to London in 1840, stored and advertised for sale, and after 

 a while thrown into the Thames. A second cargo was tried as a fer- 

 tilizer by an English farmer, and found to give such marvelous results 

 that the shipping company made good haste to contract with the Peru- 

 vian Government for the entire deposit. This article, well known as 

 guano, has held a settled value ever since its introduction, and, had it 

 come into the hands of the alchemists, it would, very likely, have been 

 presented as an elixir of vegetable life. Now, its worth is graded by 

 analysis, and is indicated chiefly by the proportion of ammonia it 

 contains. 



The absence of rain will account, perhaps correctly, for the un- 

 usual retention of the soluble material characteristic of the guano of 

 Peru ; but the formation of the nitre-heds of that region is a problem 

 in geological chemistry more difficult to determine. There are evi- 

 dences of volcanic overflow and of marine dej^osition, and the alkali in 

 the compound may have originated in either of these or other sources, 

 but neither the volcano nor the sea could furnish the nitrogen of the 

 compound. If not from organic accumulations, we seem to be referred 

 to the air as the source of nitrogen, and left to conjecture the condi- 

 tions and forces which could bring elemental nitrogen into union in 

 so great a quantity. Without pursuing these inquiries, it may be 

 permitted to cite a fact which seems entitled to consideration in the 

 case, namel}^, the conditions for an unusual overflow of atmospheric 

 ammonia in this region. It is fed by perpetual trade-winds winds 

 coming from the southeast across a wide continent of soil that is rich 

 to rankness, and warmed under a vertical sun. Coming from the 

 Atlantic and saturated with water, these winds gather the exhalations 



