1867.] MAW TEETIAEY WHITE CLAYS. 389 



minuted shells ; and I would submit whether (if the Tertiary clays 

 have been derived from the chalk) the state of impalpable subdivision 

 of the silica and alumina may not result from their having been 

 wrapped up in organic association with the carbonate of lime com- 

 posing these shells. 



A comparison between the following analyses of chalk indiscri- 

 minately collected from various sources, and the composition of the 

 white Tertiary clays of Devon and Dorset, will, I think, strongly 

 support the probabihty of the derivation of the clays from the 

 chalk. 



a. b. 



Finely divided silica soluble in caustic potash . 026 16'710 



Insoluble siliceous matter (fine clay) 6*090 



Oxides of iron and alumina 2-86 0-780 



Lime 52-33 40757 



Magnesia 0-31 0825 



Potash and soda Traces. Traces. 



Phosphoric acid Traces. 0-242 



Sulphm'ic acid Traces. 1-546 



Carbonic acid and loss 44-24 33-050 



100-00 100-000 



a. Analysis of Chalk from Gloucestershire, by Dr. Voelcker. 



b. Analysis of Chalk-marl or *' Mahn" from Wiltshire, by Dr. Voelcker. 



The following analyses are taken from the article by Prof. Thomas 

 Way and Mr. J. M. Payne " On the Chemical and Agricultural 

 Characters of the Chalk Formation," published in the 12th volume 

 of the Journal of the Eoyal Agricultural Society of England, 1851. 



Soluble in dilute acids : — c. d. 



Silicic acid (silica) 2-16 2-11 



Carbonic acid 29-96 36-73 



Sulphuric acid 0-21 0-06 



Phosphoric acid 0-21 0-05 



Chlorine 0-08 0-04 



Lime 41-52 49-16 



Magnesia 0-30 1-18 



Potash 0-26 O'll 



Soda 1-64 1-36 



Protoxide and peroxide of iron 2-20 1-74 



Alumina Oil 78-65 020 92-74 



Insoluble in acids : — 



Lime 1-71 0-22 



Magnesia Trace. Trace. 



Potash 0-32 0-15 



Soda.. 007 0-05 



Alumina and a little oxide of iron 2-57 1-42 



Silicic acid and sand 16-68 21-35 5-42 7-26 



100-00 100-00 



c. Analysis of the Grey Marl or " Malm " (No. 7) by Prof. Way. 



d. Analysis of Chalk-marl (No. 8) by Prof. Way. 



