44 Correspondence — Mr, S. V. Wood, Jan, 



ture of these valleys, and that of the Boding, where the southern- 

 most outliers of the Glacial clay occur, being those nearest to 

 the common point of inosculation of the three valleys. Unless 

 this section be wrong, I submit that if the posteriority of the 

 Thames gravel (x4 and x5) to the Glacial clay be doubtful, then the 

 posteriority of the implement graA^el at Bedford to the same clay 

 must be doubtful also ; for, so far as this relative position goes, 

 the two gravels are identical — what I contend being, that though 

 both are posterior to the Glacial clay, the Thames gravel is much 

 older than the Bedford, in the latter part only of which contention 

 Mr. Dawkins agrees with me. Palaeontological evidence is a valuable 

 auxiliary to Geological position, but cannot override it ; and if the two 

 clash, the latter, I submit, should prevail. My own belief, however, 

 is that they never really clash, and that the present case, where the 

 Palaeontology, as deduced by Mr. Dawkins from the Mammalian re- 

 mains and the physical Geology, as deduced by myself, so strictly agree 

 is an instance of this. I also ask whether this section can be recon- 

 ciled with the other of Mr. Dawkins' propositions, viz., that the main 

 features of the country were sketched out before the Glacial period ? 

 Is it not evident that the three valleys have been formed by a great 

 denudation posterior to the Glacial clay ? So far from limiting my 

 meaning of a valley to the stream itself, I contend that all the 

 valleys of the East of England, with one or two exceptions, have 

 been formed subsequently to the Glacial clay ; but I point out that 

 this clay occupied depressions or erosions of greater or less extent, 

 some of the smaller of which (as in the case of parts of the Eoding 

 and Wid valleys), have been incorporated into existing valleys that 

 chance to traverse them, quite irrespective of their original character ; 

 and thus give in these parts an illusory impression of the valley having 

 been formed before the Glacial period. I have been especially de- 

 sirous to call to the attention of geologists the great contrast pre- 

 sented, in this respect, by the valleys in strata newer than the Trias 

 south of Flamborough Head, to those of the same strata north of 

 that point. 



In reply to Mr. Green, I beg your readers to compare the section 

 he has given in his letter to you with that which he gives in the 

 Memoirs of the Geological Survey for sheet 45 (which is that 

 objected to by me in my paper), and judge for themselves what 

 similarity there is between them, for there appears to me to be 

 scarce any. If the suppositious (or dotted) line be omitted, I see 

 little in his section sent you to object to, beyond its incomplete- 

 ness ; and I ask your readers to judge what ground it affords for the 

 assertion, made in reference to the section given in Memoir 45, 

 across the Ouse, *' that a valley existed in the stratified rocks, pre- 

 vious to the deposition of the drift, which has been filled up with 

 gravel, and then partly hollowed out again." ^ I subjoin a section 

 shewing what I submit to be the true structure across the Ouse at 

 Buckingham. In it I represent the Great Oolite and Cornbrash as 

 presenting an eroded surface to the Glacial beds, which I submit 

 ^ Memoir for sheet 45, p. 34. 



