neighbourhood of Grantham. 259 



On the whole, the Great Oolite and its associated beds in their 

 extension northwards, bear a closer resemblance to the Yorkshire 

 than to the Bath and Minchinhampton series, except a portion 

 of the upper beds at Ketton and Casterton. 



For further details I may refer to the " Notice of the Geology 

 of the neighbourhood of Stamford and Peterborough," by Cap- 

 tain Ibbetson and Mr. Morris, published in the Transactions of 

 the Meeting for the Advancement of Science, 1847. When I 

 visited Lincolnshire I had not seen this interesting paper, and it 

 appears that we had independently arrived at the same conclusions. 



Great Oolite (continued) North of Grantham. 



There are some large and valuable quarries of Great Oolite at 

 Aucaster, eight miles north-east of Grantham, which have long 

 been famous for their beautiful building- stone. The following 

 section will explain its general character in descending order : — 



1 . Blue clay, in which I could detect no fossils ; perhaps the repre- ft. in. 



sentative of the Bradford clay, which in Wilts immediately 

 overlies the Great Oolite, and often separates the minor 

 subdivisions. Near the top it is traversed by a thin dingy- 

 white kind of marl, with a few imperfect impressions of plants 12 



2. Ragstone — coarse, shelly, hard oolite 5 



3. Sandy, soft (rarely shelly) oolitic freestone, variously coloured, 



yellow, pink and white, which often gives it, from its variegated 

 wavy hues, a beautiful appearance. This forms the famous 

 building-stone, and yields very large blocks 17 C 



4. Hard, shelly oolite, generally of a blue colour. Not worked . . 16 



5. Soft white stone below, depth uncertain. 



Total 50 6 



Near the above is another quarry, in which the strata above 

 the freestone are thicker, the blue clay no. 1 amounting to a 

 thickness of 20 feet, and resting upon a hard blue stone containing 

 many shells, especially a large species of Avicula, and broken 

 fragments of carbonized plants, but too imperfect to determine. 

 There is a soft, yellow, sandy band at its base also full of similar 

 vegetable remains ; — the total thickness of the two beds does not 

 exceed 2 feet. The white rag, equivalent to no. 2 in the previous 

 section, is only 1 ft. 3 in. thick, and reposes on the freestone. 



The fossils in the ragstone and freestone are small and not 

 numerous, and as I could obtain only two genera. Area and 

 Cardita, the shells of which were much waterworn, no comparison 

 can be instituted between them and the equivalent series at Bath 

 and Minchinhampton. The abundant remains of plants, and 

 their rarity in Gloucestershire and Somerset in the Great Oolite, 

 seem to indicate a closer affinity, zoologically, with the Yorkshire 

 oolites; and I am informed by my friend Mr. Lycett that he 

 and Mr. Morris could identify very few of the Great Oolite 



