1850.] BRODIE ON THE INFERIOR OOLITE. 241 



north to south along the whole of the escarpment, and at one spot 

 near the Devil's Chimney, where the freestone is thickest, it shows 

 itself about eighteen feet below the oolite marl, and is there a coarse 

 crystalline rock, mainly composed of shells and corals, a foot and a 

 half thick. The more interesting fossiliferous division of the free- 

 stone immediately overlies the Pisolite ("Pea-grit" of Murchison*), 

 and attains a thickness of seventy-five feet. It is a coarser and softer 

 oolite than the upper part of the freestone, of a yellowish-white 

 colour, and abounding in a great variety of small shells and corals, 

 many of which belong to new species, and which are strikingly con- 

 trasted with those in the superior and inferior beds. Since the free- 

 stone is traversed at irregular intervals by certain shelly layers, con- 

 taining the same characteristic fossils, and the whole evidently forms 

 one connected stratum, which has been exposed, apparently, to cur- 

 rents of water of greater or less intensity, and the shells and corals in 

 consequence more or less abraded, it will be better to adopt the term 

 '•^ shelly freestonef ," instead of "roestone," which simply means oolite. 



As the Pisolite can be followed all along the line of the escarp- 

 ment, the lower shelly beds in the freestone can be accurately defined ; 

 but the upper fossiliferous strata, from the height of the cliff, are more 

 difficult to distinguish. They may be best examined on the western 

 brow of Leckhampton Hill, where the oolite marl above, and the Pi- 

 sohte below, form very good horizons for marking the course of the 

 intervening freestone. On the north and south the freestone is much 

 reduced in thickness, and at the more southern end of the hill the 

 higher beds are not exposed ; but at the northern extremity, opposite 

 Cheltenham, the upper series is largely developed. The general and 

 true dip is at an angle of about seven degrees to the south-east. 

 The freestone and associated deposits extend for several miles along 

 the entire line of the Cotswolds, in the district now under review, 

 where they present occasional lithological variations, but are in most 

 cases equally rich in organic remains. On the whole, Leckhampton 

 Hill aifords a good type of the lower oolitic system constituting the 

 outer edge of the Cotswold chain in its range from north-east to 

 south-west across Gloucestershire, although there are, as may be ex- 

 pected, certain local distinctions in the comparative thickness, mine- 

 ralogical structure, and zoological contents of particular beds. The 

 superior strata, however, above the Trigonia grit, are not exposed at 

 Leckhampton, but occupy the higher grounds on the east, up to their 

 junction with the Stonesfield slate. 



With the permission of my friend Mr. Strickland, I subjoin the 

 following corrected section of Leckhampton Hill, from the Trigonia 

 grit to the lias inclusive. 



* Geology of Cheltenham, 1834, p. 12. sections figs. 1 & 2. 



t The term '•'■ shelly freestone^^ must be understood to apply to the lowest and 

 more fossiliferous division of the freestone just above the Pisolite, and to the other 

 shelly bands which are interspersed amongst it. The word " freestone" has been 

 already given by Sir R. Murchison to the upper part, and may therefore be used 

 in contradistinction to the above, though in common parlance it may with pro- 

 priety designate the entire sequence between the oolite marl and the Pisolite. 



T 2 



