Yol. 69.] BATHONIAN ROCKS OF THE OXFORD DISTRICT. 505 



Prom the limestones the following percentages of insoluble 

 residue, iron and alumina, were obtained : — 



Han borough 6"27 



Portland-Cement Works 4-83 



In the Great Oolite the results were more interesting, the 

 •Fossiliferous Cream-Cheese Bed having practically the same com- 

 .position in Gibraltar Quarry aa in the Ardley section. 



Residue insoluble in hydrochloric acid .. 



Ferrous carbonate 



Ferrous oxide, alumina, and phosphates 



Calcium carbonate 



Magnesin m carbonate 



Ardley. 



Gibraltar. 



Per cent. 



Per cent. 



133 j 



1-39] 



043 [ 4-58 



040 I 4-59 



2-S^J 



2-80 J 



14-38 



94-67 



039 



0-41 



The two Terebratula Beds in Gibraltar Quarry are found to 

 have a very similar composition, the percentage of clay, iron, and 

 alumina being as follows : — 



First Tcrebratuta Bed 14-94 



Second Terebratula Bed ... 16-64 



The Nerincea Kock becomes slightly more marly when traced 

 'from east to west, as the following results show (insoluble 

 residue) : — 



Per cent. 



Gibraltar 471 



Portland-Cement Works 5-04 



Ardley 5'75 



Since none of the beds below this are exposed in different 

 sections, it is not possible to institute any comparisons. In the 

 Ardley section the compact limestones of the lower part of Block 2 

 wary in containing from 90 to 92 per cent, of calcium and mag- 

 nesium carbonates. In Block 3 occur the least calcareous beds 

 of the Great Oolite ; the six beds from the Ardley section that 

 have been analysed show the following percentages of insoluble 

 residue, iron, and alumina ; the residue in Bed 22 is entirely clay, 

 but in the other beds consists chiefly of quartz. 



Per cent. Per cent. 



Bed 22 78-08 Bed 25 22-62 



Bed 23 25-32 Bed 26 5-59 



Bed 24 1667 Bed 27 20-04 



In the Fullonian of Ardley we find the following percentages: — 



Bed 29 43-69 Bed 31 Fuller's-Earth Pock 16-88 



Bed 30 41-52 Bed 34 Rhynchonella-Lioceramus Beds... 25 - 29 



In the jSTeseran Beds the percentage of clay, etc. is very high, 

 Tbeing anything between 58 and 91, except in the case of the 

 Astarte Bed, where it is only 31-24. The green coloration appears 

 'to be due to ferrous carbonate. 



2l2 



