52 



Sketch of the Geology of the neighbourhood of Grantham, Lincoln- 

 shi?'e ; and a comparison of the Stonesfield Slate at Collyweston 

 in Northamptonshire with that in the Cotswold Hills. By the 

 Rev. P. B. Brodie, M.A., F.G.S. 



Read 18th June 1850. 



The object of the present paper is to give a short account of 

 the geology of a portion of the county of Lincoln, especially in 

 the neighbourhood of Grantham and Stamford, and to point out 

 its identity in many respects with certain parts of Gloucestershire. 

 The formations observable in the district above mentioned are 

 the Great Oolite, Stonesfield Slate, and Lias. The Great Oolite 

 (and some of the superior overlying groups, including in places 

 the cornbrash) may be traced with considerable regularity from 

 Minchinhampton in this county in a north-easterly direction 

 to Stamford, whence it pursues a more northern course into 

 Yorkshire. The Great Oolite is extensively quarried at Ketton 

 and other places near Stamford, and affords a good building- 

 stone, more or less full of fossils; one bed, in which I found 

 Patella rugosa } consisting of a coarse-grained oolitic freestone 

 lithologically resembling the shelly freestone in the Inferior Oolite 

 at Leckhampton Hill. I was unfortunately so much hurried that 

 I had no time here to make sections, or to examine the quarries 

 more accurately. In a beautiful old Norman church lately 

 restored, at Tickencote in Rutlandshire, I noticed blocks of this 

 stone made up of minute shells in a good state of preservation, 

 similar to some on Minchinhampton Common. Crossing the 

 narrow lias valley to the opposite hill at Collyweston, which 

 commands an extensive view over the surrounding country, the 

 Stonesfield slate is largely quarried, and, as in the Cotswolds, 

 occupies the highest ground in the district. The following is a 

 section of one of the deepest quarries in descending order : — 



ft. in. 



1. Rubble, consisting chiefly of broken slate 5 



2. Sand, a few inches. 



3. Hard slate (ragstone) 4 



4. Yellow sand 3 



5. Slate 1 



6. Yellow sand 



7. Bluestone, with traces of vegetable matter in fragments . . 16 



8. Slate 3 



18 6 



