340 ^Tof, Sedgwick on the [May 



their zoological phenomena. It was first pointed out by Smith 

 (Farey's Survey of Derbyshire, p. 110, HI). Parkinson after- 

 wards furnished us with many interesting details, and established 

 the complete identity of the great argillaceous deposits of the 

 London basin^ and of the Hampshire coast. (Geol. Trans, vol. i. 

 p. 336). But it was reserved for Webster to describe a still 

 more important series of facts which went far to complete the 

 natural history of the two formations. The propriety of this 

 classification has been further confirmed by elaborate sections 

 taken by Bnckland and Conybeare from certain parts of the 

 London hasin,'^' (Geol. Trans, iv. 277.) Wo have been thus par- 

 ticular in enumerating authorities, because they all tend to esta- 

 blish a conclusion which it has lately been attempted to invali- 

 date. On referring to the specific objections urged against the 

 classification we have been describing, it will be seen that they 

 are all founded on the examination of a single natural section. 

 {Annals of Philosophy, p. 217, 218.) The statement contains, 

 therefore, in a great measure, its own refutation. No man Hving 

 can on such grounds judge of the propriety of any geological 

 arrangement ; still less is he entitled to assert that every thing 

 is in favour of his own opinion. It requires repeated compari- 

 sons before we can form a correct estimate of the extent and 

 relative importance of any system of beds ; and without that 

 knowledge we are not in possession even of the elements of a 

 good arrangement. 



The extraordinary vertical beds which appear in Alum Bay, 

 and are continued in the same position on the north side of tne 

 chalk range to the eastern extremity of the Isle of Wight, are 

 separated by Mr. Webster into two formations, (Geol. Trans, 

 vol. ii. pi. 11, &:c.) 



(1.) Sand and Plastic Clay. Extending from the chalk to the 

 bed of cemented pebbles marked {z.) 



(2.) London Clay. Represented" in this instance by a bed 

 (B) about 250 feet thick. 



Against this system it is urged (Annals, p. 217), that there is a 

 bed of London clay marked (d) in the same section, belovj the 

 greater part of the beds of sand and plastic clay ; that there is as 

 much apparent continuity in the bed {d)j as in the one marked 



To this we reply, that there is no apparent continuity in either 



* The pits at Catsgrove Hill, near Reading, are noticed by Dr. Woodward, an^ f 

 series of specimens collected by him from that locality, are still lodged in the cabinets of 

 the University of Cambridge. His account of the section, as it existed more than 100 

 years since, is as follows : (Cat. of Fossils, vol. ii. p. 41.) 



" The uppermost stratum is of gravel, about two feet thick. Thin clay of varies 

 colours, purple, blue, red, liver-colour, 3.S feet. Next the sand, with the oyster shells, 

 composed of grains, greenish, black, and white, one foot thick. Under tliis a duSky 

 clay, with some oyster shells in it, but very tender and rotten, a foot thick. Under- 

 5icdtli^ chalk, in which the workmen have sunk 20 feet without finding the bottom," &^. 

 He afterwards adds, that the bed of sand with oysters had been traced for two mileSj^on 

 fit^ry &lde of Reading. 



