AND HIS COTEMPORARIES. 583 



bivalve shell Gyrena fluminalis, long regarded as 'pre-emi- 

 nently preglacial,' from its presence in the Crag, occurs in 

 abundance at Erith, Ilford, Grays Thurroek, and Stutton ; and 

 from Grays Thurroek, I had determined undoubted remains of 

 JElephas antiqims, Falc, and Rhinoceros leptorhinus, Cuvier (R. 

 megarhinus, Christol), found along with Hippopotamus major, 

 free from association with Elephas primigenius, or Rhinoceros 

 tichorhinus, the two characteristic forms of the glacial de- 

 posits of Northern Europe and Siberia. The three fossil 

 mammals of Grays above-named were identified by me as 

 occurring in the Sub-Apennine Pliocene deposits of the 

 Astesan, and in the preglacial lacustrine deposits or ' forest- 

 beds ' of the Norfolk coast. The weight of the palseontological 

 evidence, molluscous and mammalian, appeared to turn the 

 scale in favour of the preglacial view. It was only when 

 Mr. Prestwich bad discovered in sections near Holderness 

 and Hull beds of clay, sand, and gravel, analogous to the 

 Thames Valley deposits, containing Gyrena fluminalis, and 

 clearly superimposed on the Boulder-clay, that the problem 

 was by him satisfactorily solved, stratigraphically, in 1860. 

 Mr. Prestwich before that time had his early convictions 

 confirmed by sections in the Valley of the Stour, at Sudbury, 

 and by a still more important case, in the Valley of the 

 Ouse, near Bedford, where a bank of gravel yielded remains 

 of Elephant, Ehinoceros, Hippopotamus, Ox, Horse, and 

 Deer. Commencing with the labours of Mr. W. Trimmer, 

 fifty years had lapsed before the point was finally settled ; 

 such a vast amount of competent observation does the solu- 

 tion of a complex geological question of this nature involve. 

 The same kind of mystery in reference to their precise geo- 

 logical age enveloped the ossiferous caves. 



It had been supposed, prematurely, by some of those who 

 had a share in the great achievements of the early days of 

 the science, that the general field of geology was swept 

 clean of all the grand questions which could command in- 

 terest, and that it would be left to those who came after 

 merely to fill in the details of the outlines which had been 

 carved by the great masters who had preceded them. Vain, 

 the complacent idea ; for even in those neglected superficial 

 sands and gravels lay buried the evidence, upon which 

 problems that now fix the attention of mankind were to 

 be worked out. Boucher de Perthes, in Prance, was per- 

 severingly ransacking the gravel heaps and gravel sections 

 of the Valley of the Somine near Abbeville, for the wrought 

 flint-weapons which are now so intimately connected with 

 his name. They had escaped the discrimination of M. 

 Baillon, one of the most active correspondents of Cuvier, and 



