1857.] BUCKMAN — OOLITES. 113 



rambles with Mr. E Hull, of the Geological Survey, during his in- 

 vestigations in the Cirencester district, we could by no means agree 

 as regarded the allocation of the upper beds of the Great Oolite ; for, 

 while I put tbis particular mass of freestone, and it is purely so, into 

 the Great Oolite division, he claims it as part of the Forest Marble. 

 My reasons for classifying this bed with the Great Oolite are as 

 follow : — 



1. It is always found to occupy a position below the Bradford 

 Clay, as long since marked by Mr. Lonsdale ; and, though this latter 

 bed is frequently wanting, yet the clays and sandy fissile slabs of the 

 true Forest Marble rest immediately on the Great Oolite in its 

 absence. 



2. These freestone-beds form an unbroken series, frequently with- 

 out even a clay-parting to the Fuller's Earth, for the thickness of as 

 much as 1 20 feet, which has been so often proved in well-sinking in 

 the Cirencester district. To divide a freestone-rock in the middle 

 seems therefore hardly warranted, unless marked by some distinctive 

 fauna of a decided kind, which, as far as I know, has not even been 

 pretended ; so that neither lithological structure nor fossil contents 

 warrant this division. 



3. The sudden appearance of clays and shales upon a freestone 

 rock, as is the case with the Fuller's Earth upon the Inferior Oolite, 

 and the Bradford or Forest Marble Clay on the Great Oolite, and 

 more especially when accompanied by such a decidedly different 

 fauna as the Bradford Clay presents, all argue such a physical 

 cbange as fully to justify a division. 



4. The Bradford Clay, where present, introduces so many new 

 fossil forms, — many of which belong also to the Forest Marble, as 

 laid down by myself, yet do not descend into the oolite-bed in 

 dispute, — that both upon physical and fossil evidence, I claim for 

 the Great Oolite all the mass of freestone between the Fuller's Earth 

 below and the Bradford or Forest Marble Clays above. 



Now, unless such a plan of division be adopted, the base-line of 

 the Forest Marble is made arbitrary ; for, although it is true that 

 these upper beds are affected to a greater or less extent by oblique 

 lamination, this is a most unsafe guide, inasmuch as the whole of 

 the Great Oolite is at places liable to this, and even the large blocks 

 of Box (Bath) oolite are formed of oblique laminae, which would 

 result in a shattered obliquely-cleaved rock if quarried near the 

 surface ; but the great value of Box stone results from its being 

 mined from galleries, and not quarried in open work, when all the 

 Great Oolite beds split up more or less obliquely. 



Again, the same bed differs widely according to the nature of the 

 band upon its surface ; hence, if the yellow Bradford Clay rests upon 

 it, it is a lightish yellow stone, splittiug obliquely some months or 

 years after an exposure, as in the road-cutting at Tetbury Road Sta- 

 tion ; the same is the case where the yellow Forest Marble clay rests 

 upon the oolite, as in the section at the Royal Agricultural College. 

 These blocks, however, were hard and compact when first quarried, so 

 much so as to render blasting necessary ; but at Chesterton, and again 



VOL. XIV. PART I. I 



