244 THE CANADIAN NATURALIST. [Sept. 



another, in each of the three great divisions of nature, and 

 handed on, from the world of vegetable existence to that of 

 animal life, before being finally returned to inorganic nature, 

 thenceforth to be subjected to a number of chemical changes, 

 preparing them for a new round of usefulness. But, in 

 order to enable this great principle to operate completely and 

 effectually, one thing is necessary ; for, owing to the concen- 

 tration of populations in towns and cities, one link, so to 

 speak, in the chain, becomes faulty, and the return of phos- 

 phates to the soil must be aided by artificial means. 



From whatever lands vegetable matters are removed in 

 the annual crops, there is a constant withdrawal of the neces- 

 sary mineral constituents of the plant, including, of course, 

 the phosphoric acid ; and, although poor or exhausted lands 

 do not shew the entire absence of phosphates, yet they have 

 become deficient in such phosphorus salts as are available for 

 the use of the growing plant ; and do not, especially, contain 

 enough to suffice for the cereals, containing, as they do, a 

 larger proportion of phosphoric acid than any other family of 

 plants. 



The grain of wheat contains about 8-lOths per cent, of 

 phosphoric acid, which proportion amounts to 16 lbs. of the 

 acid to each ton (=2,000 lbs.) weight of wheat. Now the 

 amount of phosphoric acid in soil may said to average 0*2 per 

 cent. ; although, except in clays the proportion is usually 

 less. Taking 0*2 per cent, as the average quantity, and 

 assuming the specific gravity of soil to be 2.5, there exists in 

 the soil covering one acre of land, to the depth of 12 inches, 

 about 68.6 lbs. of phosphoric acid ; or only enough to supply 

 the phosphates to 4.16 tons of wheat. The total weight of 

 wheat, (whether as grain, or in the state of flour) exported 

 from the port of Montreal ni 1869, amounted to about 

 292,534.5 tons* ; or a weight requiring the total abstraction 

 of phosphoric acid from 70,320.8 acres (=109.8 square 

 miles) of good average land. This withdrawal of phosphoric 



* This information was kindly famished by TVm. T. Patterson, Esq , 

 Secretary to the Montreal Board of Trade. 



