1864] CHEMISTRY OF MANURES. 105- 



Soluble phosphate 22 to 25 per cent. 



Insoluble phosphate 8 " 10 " " 



Water 10 " 12 " " 



Suli)hate of lime 35 " 45 " '' 



Organic matter 12 " 15 " " 



Nitrogen 0-T5 to 1-5 per cent. 



" If sufficient sulpliuric acid were used to decompose the whole 

 of the phosphate of lime, the product would be too wet to be pack- 

 ed in bags, and would require either to be mixed with extraneous 

 substances of a dry and porous nature, or to be artificially dried. 



" The price of the best descriptions of superphosphate ranges 

 from 5/. 15s. to 61. 10s. per ton, and of that made from purely 

 mineral phosphate from 4:1. to 5^ 5s. per ton." 



Of the raw materials annually worked up into superphosphate 

 in Great Britain, Mr. Lawes estimates that about half is derived 

 from the deposits of fossil bone-earth, or coprolite, discovered of 

 late years in several parts of England. Bone-ash, chiefly imported 

 from South America, animal charcoal from Germany, and bones 

 from all parts of the world, together supply about forty per cent 

 more of the raw material ; while the remaining ten per cent of the 

 total supply is made up by guano (chiefly of the less nitrogenous 

 and more phosphatic kinds), with a little apatite (say 200 to 500 

 tons per annum), obtained from Spain, Norway, and America. 



Importation op Manures into Great Britain. — These 

 data alone might serve to indicate that the industry of manures,, 

 since the impulse it received in 1840, has afibrded occupation not 

 only to the inventive and manufacturing, but also to the commer- 

 cial activity of the English nation. But of this the origin and de- 

 velopment of the guano-trade afibrds direct evidence. 



[Here follows an historical sketch of the growth of the trade in 

 guano, from which we learn that the first experiments with this 

 manure in England appear to have bsen made from 1838 to 1840. 

 Messrs Gibbs & Sons, its principal importers, commenced in 1842 

 by importing 182 tons of guano.. In 1843 they imported 4667 

 tons, and in 1862 their total supplies (as well for foreign as for 

 British consumption) equalled no less than 435,000 tons. Of this 

 between one-third and one-fourth was retained for use in the United 

 Kingdom. Its price, which has varied from dl. to 15/., is now 

 about 121. the ton.] 



The extraordinary success ^of the Peruvian guano-trade led to 

 voyages of discovery in search of fresh deposits ; several of which 



