66 



am informed by the engineer of the works that the deposit presents a similar cha- 

 racter at Bletchley, distant three miles from Loughton, and seven from Thorp. 



I have spoken of a bed of clay which prevails throughout the whole line, with 

 the exception of one point, the acclivity to the south of the valley of the Ouse, 

 where it is less cleaily denned. Now this stratum, although it occurs in what is 

 denominated the Oxford-clay formation, presents characters which clearly prove 

 that it has no connection with that deposit. It generally presents an uniform ap- 

 pearance, being a hard, dry clay, of a very dark blue colour, occasionally breaking 

 down in very large masses. Nodules of chalk, from the size of a pin's head to 

 two or three inches in diameter, occur in great numbers, pretty regularly distri- 

 buted throughout it. These are always rounded and smooth, and numerous flints 

 are associated with them. The most interesting fact, however, is the number and 

 variety of the fossils found in this deposit. These consist principally of Ammo- 

 nites, of at least from fifteen to twenty species ; numerous specimens of Gryphcea, 

 dUitata and incurva, especially the former ; Belemnites, portions of Pentacri- 

 nites, several kinds of Terebratula, and specimens of Ostrea and Serpula. I 

 have one specimen of Echinus, which is filled with chalk, and, though very much 

 worn, exactly retains the appearance of the chalk fossils. Many of the fossils are, 

 indeed, worn, others are broken ; the fragments of Ammonites are particularly 

 numerous, and are often covered with indurated clay, or limestone, which has 

 been worn round and smooth by the action of water. Beds of sand and gravel 

 frequently occur through the deposit, and in them are found numerous small spe- 

 cimens of Ammonites and univalve shells, most of which are composed of iron 

 pyrites. A few saurian vertebrae have also been discovered. 



Now it is very evident that this deposit has little in common with the Oxford 

 clay, although traversing the whole breadth of the formation so designated ; for, 

 in addition to the peculiar fossils of that deposit, we here find those of the Chalk, 

 Lias, and Oolites. The fossils of the Oxford clay, it is well know, are frequently 

 much compressed, and, when they are of a delicate structure, preserved with diffi- 

 culty. This is especially the case with the Ammonites. Of these, as also of 

 Gryphcea dilitata, (a characteristic shell), I have several specimens from New- 

 port Pagnel, four miles east of the railway, and from Willan, one mile to the 

 south of Newport, where the deposit bears the true character of the Oxford clay. 

 Here, also, I have found very beautiful remains of the Ichthyosaurus. The 

 fossils, however, in this formation, are generally very few : in this respect forming 

 a striking contrast to those discovered in the railway cuttings. 



Without offering any theory upon the subject, there is abundant evidence for 

 the following conclusions. That, although supposed to form a part of the Oxford 

 clay, the formation I have attempted to describe is of a totally different character ; 

 that it is posterior in its deposition to the Chalk formation ; and that its fossils 

 have been brought from a distance : and from all the circumstances of the case, 

 it seems to be undoubtedly a deposit of diluvial origin. 



