1866.] SEELEY DRIFT OF THE PENLAND. 475 



bridge. Those now to be noticed are in its more immediate neigh- 

 bourhood. 



East of Cambridge the fine flint-gravel reaches, by Granchester 

 and Comber ton, nearly as far as the Eoulder-clay of Stow, being 

 here deposited on the Gault. 



North of Cambridge it extends in a continuous bed by Barnwell, 

 Chesterton, Histon, Oakington, Long Stanton, Landbeach, Water- 

 beach, Denny Abbey, and in a less continuous belt nearly all the 

 way to Ely. At Comberton, teeth of the Tichorhine Rhinoceros 

 have been found ; but it is only from a few pits that bones can 

 be collected, though at BarnweU and Chesterton they are not rare. 

 I have found shells in the gravel under the Observatory on the St. 

 Neots Road, at Barnwell, Chesterton, and Oakington ; but in every 

 case they were land or freshwater forms, though from the gravel of 

 Waterbeach the Woodwardian Museum has a vertebra of a whale, 

 which, from its preservation, was evidently contemporaneous with 

 the formation of the bed. It has lost its epiphyses, and is seemingly 

 worn. 



At and beyond Trumpington the gravel is remarkable for the great 

 extent to which its upper 2 or 3 feet are contorted and folded, 

 as though by lateral pressure. Except in some so-called brick- 

 earths near Hadleigh in Suffolk, I never saw more marked instances 

 of the kind on a small scale. But the gravel-flexures may only in- 

 dicate the site of an ancient forest. 



About Cambridge the chief pits are at Barnwell and Chesterton, 

 where the gravel often shows a large amount of false bedding, which 

 varies greatly from year to year. 



This gravel consists chiefly of small flint-fragments, generally with 

 sharp angles, often with the angles rubbed off ; and rarely specimens 

 may be found which are well rounded. It is no uncommon thing 

 to find a flint well worn on one side, but with the others showing 

 fractured surfaces, which fact clearly indicates that the flint was 

 already a worn and drifted boulder before broken up to form gravel. 

 Phosphatic nodules and shells of the Greensand are not rare ; and 

 many of the smaller fossils of the latter bed may be found in the 

 Barnwell gravel in vast numbers. Upper Chalk fossils are common. 

 Lias gryphites, greatly worn, are numerous ; and the Oxford-clay 

 gryphites in fragments are not rare. I have found some corals like 

 those of the Coral Rag. The rock-specimens which have come 

 from great distances are rarely large. The largest block which I 

 have seen from Barnwell, measured about a foot and a half in 

 each diameter, and was probably from the Shanklin Sands. Jas- 

 per conglomerate is found in angular blocks of a few inches dia- 

 meter. Granites of various kinds, syenites, and traps of various 

 characters, some of them amygdaloid, are among the common ''ig- 

 neous " rocks, occurring in partly rounded boulders from 3 to 

 about 9 inches in diameter. There are fragments of Oolitic Lime- 

 stone. But all these are comparatively rare, and might pass un- 

 noticed, but that in sifting the gravel they are necessarily thrown 

 out. At Chesterton they are much more abundant than at Barn- 



