Fish Manures, 1-5 



price both sulphuric acid and lime. Potash when wanting may 

 be supplied to the soil by wood-ashes, but phosphoric acid and 

 ammonia are less easily obtained and command higher prices. 



An abundant supply of phosphate of lime is found in bones, 

 which when dried contain from 50'0 to 6O0 p. c. of mineral mat- 

 ter, consisting of phosphate of lime, with a little carbonate, and 

 small portions of salts of magnesia and soda. The remainder is 

 organic matter, which is destroyed when the bones are burned. 

 This phosphate of lime of bones contains 46*0 per cent of phos- 

 phoric acid, and the refuse bone-black of the sugar-refiners usually 

 affords about 32'0 per cent, of the acid. The different guanos 

 also contain large amounts of phosphoric acid, and that known as 

 Columbian guano is principally phosphate of lime. Various de- 

 posits of mineral phosphate of. lime have of late attracted the at- 

 tention of scientific agriculturists. I may mention in this connec- 

 tion the crystalline phosphate of lime or apatite of our Laurentian 

 limestones, and the phosphatic nodules found in different parts of 

 the Lower Silurian strata of Canada and described in previous Re- 

 ports. 



These mineral phosphates are in such a state of aggregation, that 

 it is necessary to decompose them by sulphuric acid before apply- 

 ing them to the soil. The same process is also very often applied 

 to bones ; for this end the phosphate of lime in powder is to be 

 mingled with nearly two-thirds its weight of sulphuric acid, which 

 converts two-thirds of the lime into sulphate, and leaves the remain- 

 der combined with the phosphoric acid as a soluble super-phos- 

 phate. In this w T ay, the phosphoric acid may be applied to the 

 soil in a much more divided state, and its efficiency is thereby 

 greatly increased. Even in its soluble form however, the phos- 

 phoric acid is at once neutralized by the basic oxyds in the soil, 

 and Mr. Paul Thenard has lately shown that ordinary phosphate 

 of lime, when dissolved in carbonic-acid water, is decomposed by 

 digestion with earth, insoluble phosphates of iron and alumina be- 

 ing formed, which are a^ain slowly decomposed by the somewhat 

 soluble silicate of lime present in the soil and transformed into 

 silicates with formation of phosphate of lime. It is probable that 

 alkaline silicates may also play a similar part in the soil. These 

 considerations show that the superior value of soluble phosphate of 

 of lime as a manure, depends solely upon its greater subdivision. 

 A portion of the phosphoric acid in Peruvian guano exists in a 

 soluble condition as phosphate of ammonia. 



