50 CHEMICAL MANURES. 



The Phosphate of Lime. For twenty years no other source was 

 known for phosphate of lime than the bones of animals. It is cer- 

 tain, if we had no other source, its use could not become general. 

 But it is not so. We know that phosphate of lime forms a part of 

 all volcanic rocks, and that in several countries there are sources of 

 inexhaustible richness. 



In the environs of Logrosan, in Estremadura, there are eight or 

 ten veins, over an extent of 1000 feet, seventy or eighty-five per cent, 

 rich in real phosphate, and whose full extent is not known. There 

 are others in Canada and Sweden. 



Phosphate is found in most marls. Considerable, deposits have 

 been found underlying cretaceous earth, which have become the 

 object of a regular working in the departments of Ardennes and 

 Moselle. Although not so rich as that at Estremadura, this de- 

 posit contains from sixteen to eighteen per cent, phosphoric acid. 



There need be no uneasiness with regard to the phosphates : their 

 price will rather be diminished than increased. 



Potash. The sources from which we can draw potash are three in 

 number : 



First, Volcanic rocks, which constitute entire chains of mountains, 

 and which contain fifteen per cent. 



Second. The waters of the sea, from which we now extract it with 

 remarkable facility by the admirable method of M. Balerd, and 

 which would be sufficient, in case of need, for all our wants. 



The deposits discovered at Strasfiirth in Prussia four or five years 

 ago are inexhaustible, and from 2000 to 3000 feet thick, spread over 

 an undetermined extent. These deposits, which are attached to a forma- 

 tion of fossil salt, authorise us in believing that this discovery cannot 

 but become general, since the deposits at Strasfiirth are sufficient for 

 several centuries, and after them we will have long chains of moun- 

 tains and the waters of the sea. 



Azotic Matter. Here, I confess, if we were condemned to employ 

 only ammoniac and nitrate compositions, there would be apparent 

 reason in saying that the actual sources known are insufficient, but 

 new sources are added to these. I will cite, for example, the fabrica- 

 tion of coke, which is done in the open air ; it will only be necessary 

 to make it in furnaces to draw considerable quantities of ammonia 

 from it. 



But if all three sources failed, we have still the azote of the air. 

 My attention has long been directed to this point. 



I have said that some plants draw their azote from the air, while 

 others find it in the soil. , From this, consequently, there is the possi- 

 bility of coming to the aid of the second by the help of the first. 



This method is already applied in culture. Green manures are 

 only valuable from this fact. It is then possible to make them gen- 

 eral, and to make them more efficacious is to push the yield of plants 

 which draw azote from the air to the utmost limit. I will cite lucerne 

 as an example, which draws from 266 to 355 pounds the acre of azote 

 from the air, which would be sufficient to enrich at lenst 9.1.1 acres 

 cultivated in wheat. Thus, if all other sources of azotic mutter were 



