1853.] DE LA CONDAMINE — DRIFT IN HUNTINGDONSHIRE. 271 



2. On a Freshwater Deposits the "Drift" 0/ Huntingdon- 

 shire. By the Rev. H. M. De la Condamine, M.A., F.G.S. 



In the Cambridge Philosophical Transactions for 1844, Mr. Brodie 

 noticed the occurrence of recent species of laud and freshwater shells, 

 associated with the bones of extinct mammalia, in the marl and sand 

 of the drift near Cambridge. The object of the present paper is to 

 describe a very similar deposit in the valley of the Ouse, between 

 St. Ives and Huntingdon. 



The district consists of Oxford clay, capped by a variable covering 

 of boulder clay (the " brown clay " of Prof. Sedgwick), which is 

 frequently concealed in the low grounds by the ordinary flint-gravel 

 of the eastern counties, this again underlying the modern alluvium 

 (see fig. 1). The gravel is worked at Hemingford Abbots, and where 

 the railway crosses the Ouse the section shown in fig. 2 is exposed. 



The surface of the Oxford clay, at the bottom of the pit, is encum- 

 bered with concretions and fossils of that formation, and supports 

 numerous boulders of granite, gneiss, trap, sandstone, mountain lime- 

 stone, oolite, flint, &c., some rounded, others perfectly angular, and 

 reaching 3 feet in diameter. No scratches are observable on any of 

 them, but their form, magnitude, and variety at once refer them to 

 glacial action. 



On the stratum of boulders rests a coarse gravel, not varying from 

 the ordinary flint-gravel of the eastern counties, with abundant frag- 

 ments of the older rocks, and containing, as usual, mammalian re- 

 mains. I succeeded in obtaining portions of Bos, Sus, Equus, and Red 

 Deer. Many of the flints are scarcely waterworn and retain their 

 chalky coating ; others are perfectly waterworn, though none present 

 the appearance of eocene pebbles. Most of them are yellow through- 

 out, but I have examples of every intermediate state of decomposition, 

 from that to the black flint apparently fresh from the chalk ; yet the 

 former are not invariably the most waterworn. It is evident, there- 

 fore, that decomposition is not a measure of the time of exposure 

 only, but must depend upon the circumstances of exposure*. The 

 crevice§ of the flints sometimes bear remains of Serpulse, and I have 

 not unfrequently observed a calcareous incrustation resembling that 

 which is common on the sea-shore ; but no shells or other marine 

 remains have been noticed in any part of this widely spread gravel. 

 I cannot therefore but think that it is not the result of ordinary 

 marine action, and that we must refer it to a sudden and violent 

 agent, hurrying along the materials of distant and various coast- 

 lines, and partly confusing them with the still more heterogeneous 

 boulder accumulations. The presence of the remains of land 

 quadrupeds must, I think, be referred to some such desolating action, 

 their remarkable abundance, in the utter absence of marine exuvise, 

 being imjirobable in an ordinary marine deposit, and without parallel 

 in any earlier formation. 



On the gravel rests a bed of coarse sand, diagonally stratified, and 



* A notable example of this is the Shooter's Hill gravel, which consists of well- 

 rounded but discoloured pebbles, with a mixture of black uninjured eocene pebbles. 



