364 . MR. A. STRAHAN ON A PflOSPHATIC 



Ciply Chalk. Taplow Clialk. 



M. Peterinann. Mr. Player. 



Moisture "7 



Organic matter 2*83 2*3 



Lime 53-24 537 



Magnesia 0'12 



Iron oxide | ^ ^-. 0-1 



Alumina ( ^'^^ OS 



Potash I ^ Q 0-1 



Soda / ^'^^ 0-2 



Carbonic acid 28-10 28-7 



Sulphuric acid 0*89 0-7 



Phosphoric acid 11-66 11*6 



Silica and sand 1-96 (Silicic acid) 0-5 



Pluorine 1 ^ 0*7 



Chlorine f ' ' traces. 



100-00 100-1 



M. Cornet calls attention to the large proportion of nitrogenized 

 organic matter which the greyish brown phosphatic chalk contains, 

 and attributes to this substance a peculiar smell evolved when the 

 rock is treated with hydrochloric acid. In this respect also the 

 Ciply Chalk resembles thut of Taplow. 



The Ciply phosphatic chalk is not rich enough to be worked at a 

 profit in its raw state, but b}^ simple mechanical processes, either by 

 dry or wet methods, a product is obtained which contains from 40 

 to 50 per cent, of phosphate. It has also, where it has been 

 naturally subjected to the action of soil-water, furnished a reddish- 

 yellow powdery material, known as " rich phosphate," which occurs 

 in pockets in the phosphatic chalk, and contains from 45 to 67 per 

 cent, of phosphate of lime, the concentration of the phosphate having 

 resulted from the removal of the more soluble carbonate of lime. 



In hand-specimens the rich phosphatic chalk of Ciply cannot be 

 distinguished from that of Taplow. Under the microscope, how- 

 ever, there are considerable differences, the brown colour and the 

 phosphate of lime being confined to a number of generally shapeless 

 pellets, while recognizable foraminifera are comparatively scarce, 

 white, and non-phosphatic. The brown grains include angular chips 

 of teeth and bone, but are more generally rounded or subangular. 

 The chemical reactions resemble those of the Taplow Chalk. 



In conclusion I may point out that there seems to be no reason 

 why the Taplow deposit should not be as valuable as that of Ciply 

 and Doullens (excluding the pockets), if it is not of too limited 

 range. Both at Doullens and Ciply the richest phosphate occurs in 

 pockets, but at the latter place the phosphatic grains are to a great 

 extent separated from the carbonate of lime by washing. The 

 friability of the Taplow Chalk would render it well adapted to this 

 treatment, and the fact that the specific gravity of the phosphatic 

 grains ranges from 2*7 to 2-8 — that is, considerably above that of 

 ordinary chalk — would facilitate their separation. It should be 



