AND THE PHOSPHATIC BEDS NEAR MONS. 



331 



The beds A^ and A" are not continuous, but in one or other in the 

 Mesvin quarry numerous breaks occur. The brick-earth A often 

 rests upon A", and even on B. 



B. Lower stage of the Landenian system, consisting of grains of 

 quartz and glauconite cemented by a more or less abundant 

 argillaceous matrix. Underneath there is a bed containing 

 black flint pebbles and nodules derived from the Chalk. 



The natural colour of stage B is dark greenish-blue, but at many 

 })laces it has acquired a yellowish ferruginous tint, in consequence 

 of the alteration of the glauconite. 



d^. Brown phosphatic chalk without flints, containing many fossil 

 shells, the shells consisting of carbonate of lime. 



cZ•^ Brown phosphatic chalk with flint nodules, scattered or 

 arranged in continuous layers. Also numerous fossils with the 

 shells of carbonate of lime, and sponges changed into flint. 



PR. A yellow -brown, powdery rich phosphate ; its chemical com- 

 position given above. It fills pockets, whose walls, formed by 

 the brown phosphatic chalk, are sharp, clean, and without any 

 transition between the two substances in contact. Eossil shells, 

 - such as the Belemnitellcr and Oysters, are often cut through 

 by the line of separation, and only the portions of those shells 

 that are imbedded in the chalk are preserved ; the parts which 

 should have been prolonged into the rich phosphate do not 

 exist. The fossil remains found in it are only siliceous sponges, 

 teeth and vertebrae of Sharks and of Saurians, Hainosaurus, 

 Mosasaurus, &c. Nodules of flint also occur, similar to those 

 found in the Chalk d^. 



Fig. 6.—i/orizontcd Section \ 

 in Fig. 5. 



the plane indicated hy the line x-y 

 (Scale 1 : 500.) 



The pockets represented in figs. 5 ajid (J were from 40 to 

 50 feet in maximum diameter, and from 20 to 25 feet in depth ; 

 but some have been discovered of much larger dimensions. Several 

 of them have furnished nearly 2000 tons of rich phosphate. 



It seems evident to the author of this paper, and it is likewise the 

 opinion of all the geologists who have studied the deposits just 



