18 



CHEMICAL MAXUEES. 



TABLE v.— ANALYSES OF PAS DE CALAIS PHOSPHATES. 



I'Jws-phate. 

 Nabringhem. Fiennes. 



Moismre at 100° C. . 



Matter volatile at a dull red heat 



Phosphoric acid (1) 



Sulphuric acid . 



Carbonic acid (2 



Fluorine (3) 



Lime 



Magnesia . 



Alumina . 



Oxide of iron 



Silica 



Deduct oxygen equal to the fluorine . 



Undetermined and loss . 



Total 



(1) Equal to tribasie phosphate of lime 



(2) Equal to carbonate of lime 



(3) Equal to calcium fluoride . 



3. Meuse, Ardennes and La 2Iarne Phosphates. — The phosphates 

 exploited in this district come almost entirely from the base of the 

 cretaceous (Greensand). This formation forms almost a continuous 

 zone which extends over 187 miles from the department of Ardennes 

 as far as Yonne, crossing those of la Meuse, la Marne and the 

 Haute Marne and Aube. It consists mostly of one, sometimes of 

 two beds of nodules of phosphate of lime, of a thickness of 6 to 8. 

 inches, but in certain districts it thins out so much as to be 

 no longer workable, the phosphate disappearing entirely, or not 

 existing in sufficient quantity. The existence of Greensand noduies 

 in les Ardennes was first pointed out in 1842 by Bauvage and 

 Bauvignier, and their chemical composition was determined in 

 1852 and 1853 by Meugy. The first extraction works were under- 

 taken by Desailly in 1856 and are still in existence. But, in a 

 general way, the works are very unstable, the sheds removing as 

 soon as the dead ground becomes too powerful, oi- the nodule bed 

 thins out. The Meuse nodules have much the same appearance 

 and composition as those of the Boulogne district ; their phosphoric 

 acid content generally varies from 14 to 20 per cent; it rarely 

 exceeds the latter limit. Sometimes they are small, sometimes 



they reach or exceed the size of an ostrich's e^rg ; thev exhibit ir 



oo 



regular contours into the spaces between wh'ch a green argillaceous 

 sand penetrates, which forces them to be broken in bulk so as to 

 clean them. At other times the phosphate of lime instead of being; 



