of the Inferior Oolite. 171 



Cotteswold sections arc of a small and imperfect character, con- 

 sisting chiefly of cuttings of rock upon deep lane-sides, or upon 

 the banks of water- courses ; and although these in the aggregate 

 exhibit the entire physical features of the deposit, they do not 

 enable us to ascertain the thickness of the whole, in particular 

 localities, with any near approach to accuracy. We can there- 

 fore only estimate the thickness by tracing upwards the beds 

 upon hill-sides, and occasionally by examining the rock brought 

 up during the process of well-sinking. From information ob- 

 tained in this manner, it would appear that the thickness of the 

 sands varies in the middle Cotteswolds from 35 to 80 feet ; and 

 Mr. Hull has shown that over the northern and southern Cottes- 

 wolds they present even a greater amount of variability in thick- 

 ness. My own observations lead to the conclusion, that, like 

 the mass of the Inferior Oolite generally, the thickness is greater 

 upon the outer western escarpment of the Cotteswolds than in 

 the interior valleys, where they are far remote from the outer 

 range. In tracing upwards the beds from the Lias there occurs 

 the following general order of succession : — 



A. Upper Lias clay, grey or blue, soft, and clearly distinguished 

 from 



B. Brown or chocolate-coloured, marly, micaceous sandstone, 

 with frequent red ferruginous stains between the lamination ; 

 occasionally the stone is more argillaceous, and buries the 

 hammer when struck; in other instances, from the presence 

 of portions of shells, it is more hard, but is peculiarly irre- 

 gular and uncertain both in hardness and colour, varying 

 from a blackish-grey to a bright foxy or reddish hue, every- 

 where glittering with micaceous particles. At about 4 feet 

 from the base are usually one or two thin bands charged with 

 fossils, the greater number of which are very imperfectly pre- 

 served : this may be designated as the lower shelly zone, and 

 may be studied in small lane-side sections at Nailsworth and 

 at Brimscombe. In the Yorkshire exposition of the deposit, 

 I shall subsequently show that a shelly zone occurs in a similar 

 position. Passing upwards from 10 to 20 feet, there occurs 

 a general diminution of compactness in the rock, and of its 

 marly structure ; there gradually sets in 



C. Micaceous, foxy-coloured or yellowish, incoherent sands, 

 seldom much compacted, but locally becoming soft sandstone, 

 from 20 to 40 feet, abruptly terminated upwards by 



D. Concretionary marly bed, usually darker in colour than the 

 sands, but varying much in structure and aspect within short 

 distances, and everywhere more or less fossiliferous ; the tests 

 of Mollusca are less frequently preserved than in the lower 



