ANNIVERSARY ADDRESS OF THE PRESIDENT. CXXXV 



hailing the discovery of a coal- deposit under London or in its neigh- 

 bourhood, the penetrating powers of his mind have been fully esta- 

 blished by these practical results. 



One of the papers contributed by Professor Phillips has a close 

 relation, in one respect, to those I have last noticed, as it endeavours 

 to explain the physical conditions under which some of the strata of 

 Shotover Hill, near Oxford, have been deposited. Tracing the his- 

 tory of discovery in respect to these deposits from 1722 to 1827, it 

 appears that the sandy strata which on this detached hill rest on 

 the Portland series, and with their associated ochres have received 

 the general title of Ironsand, being by Conybeare referred to the 

 Hastings group, had, until the latter date, afforded no organic 

 clue by which the physical circumstances under which the deposits 

 had been formed could be inferred. Dr. Pitton then ascertained the 

 occurrence of Purbeck deposits at "Whitchurch in Buckinghamshire ; 

 and about 1832, the Rev. H. Jelly discovered Paludiniform shells in 

 the sands of Shotover ; and this discovery, confirmed by Mr. H. E. 

 Strickland, was published by Dr. Pitton in his well-known memoir 

 " on the Strata below the Chalk." Mr. Strickland added a Unio ; and 

 Professor Phillips himself has still further added to the list of fossils 

 which I will call physically characteristic. The word " Portland" 

 is in the mind of most geologists associated with the idea of the 

 " Portland Limestone ;" but the words " Portland Rocks " have a 

 much wider acceptation in this paper of Professor Phillips, and refer, 

 not alone to a calcareous form of deposit, but to the green sands, 

 clay-bands, and layers of subcalcareous concretions, rich in fossils, 

 which here mark more than the age of a deposit ; for, whilst the fossils 

 Pecten, Perna, &c, mark the aggregate of 70 feet in thickness to 

 have been marine, another overlying group of strata, about 80 feet 

 thick, consisting of various coloured but not green sands, bands of 

 clay, layers of peroxide of iron, and cherty masses, is as decidedly 

 marked to have had a partially freshwater origin by Unionidce, 

 Paludince, and other mollusca, which, though some may be considered 

 as possibly marine, mark distinctly at least the cooperation of fluvia- 

 tile action, and, combined together, establish the existence of an 

 estuary- rather than a lacustrine formation. Professor Phillips there- 

 fore infers that the Shotover Sands are a northern equivalent of the 

 Hastings Sands ; but, from the difference in the species of Unionidce, 

 he suggests the probability that the river which was the cooperating 

 agent in producing the deposit was a different stream from that of 

 the typical Wealden, and that its effects wiU be traced much further 

 to the north-eastward. Without doubt, these deductions from facts 

 are deeply interesting ; but what a wide field they open for specula- 

 tion, since, the course of the river being traced by its effects, its 

 banks are yet to be discovered ! I cannot help also observing that the 

 species of Unionidce appear to be remarkably local, or at least that 

 the variations in form from one locality to another are so great as 

 to render them admirable guides in distinguishing one estuary from 

 another belonging to the same epoch, but not equally so for estimating 

 the relative ages of deposits, — a remark which has been strongly im- 



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