530 
THE CRETACEOUS ROCKS OF BRITAIN. 
A sample of the layer which breaks into columnar or rectangu¬ 
lar pieces at the base of this zone in Lincolnshire, was analysed 
bv Mr. Grant-Wilson, of the Geological Survey, wdth the following 
result *: — 
Insoluble in hydrochloric acid, chiefly alumina - - - 1.06 
Soluble portion— 
Carbonic acid.43.05 
Sulphuric acid - -- -- -- - .45 
Lime - - - - - - - - - -54.63 
Magnesia - -- -- -- -- .39 
Manganese - .trace 
Protoxide of iron -------- .35 
Alumina ------- .24 
100.17 
These ingredients may be combined as follows : — 
Carbonate of lime.- - 96.88 
Carbonate of magnesia - - - • - - - .81 
Sulphate of lime - - - - ----- - .76 
Alumina and iron oxide ------- .59 
Insoluble silica and alumina.1.06 
* 
100.10 
The following analysis of chalk is taken from a ‘‘Reporton the 
Soils of Kent and Surrey to the Technical Education Com¬ 
mittees/ ’ by A. D. Hall and F. J. Ply man, of the Agricultural 
College at Wye (1902). Mr. Hall informs me that the sample 
came from a pit about three quarters of a mile east of Wye, and 300 
feet above the outcrop of the Gault. The chalk was dried at 100° C. 
Insoluble Residue - - -.2‘480 
Soluble — Lime -------- 52750 
Magnesia - - - - - - - - *211 
Ferric Oxide -------- *067 
Alumina - - - - - - - - 413 
Potash . - -098 
Soda ------ .. - - -013 
Oxide of Manganese ------ 449 
Soluble Silica ------- *035 
Sulphuric Acid ------- -082 
Phosphoric Acid - - - - - - 406 
Chlorine -------- -006 
t Carbonic Acid - - - - - - 37‘670 
+ Organic matter and combined water - - - 5‘400 
99480 
* Quoted from the Geology of East Lincolnshire. Man. Geol. Survey, 
1884. 
t Equal to 85‘61 of Calcium Carbonate. 
1 Mr. Hall informs me that most of this amount is probably organic 
matter, and that the combined water is not likely to exceed 1*5 per cent. 
