4Q Correspondence. 



formation as mucli newer than the Drift as is implied by its occupa- 

 tion of a trough ciit down, in its deepest part to more than 500 feet from 

 the upper Drift ; and because it is also in intimate connexion with the 

 disturbances under which the Thames gravel .emerged. In the sec- 

 tions I gave in your Magazine, space necessitated this being shewn 

 as a vertical drop, but in reality it arises from a pitch in a north-west 

 direction, as the following detailed section shows : — (See Woodcut, 



These are instances in which actual ocular evidence of violent 

 dislocations is obtainable. There are many more which are deduci- 

 ble from the structure of the crag and Drift, and I believe that many 

 of the sections in these upper beds which present perplexing features 

 are due to this cause. Thus the capping of Boulder-clay which rests 

 on the Chillesford beds, at Chillesford, and which Mr. Fisher, in his 

 paper, read before the Geological Society, brought into his evidence 

 of " trail," I believe is nothing but an oblique throw of the upper 

 Drift, on to the Chillesford beds ; for in a pit, only a furlong and a half 

 north of this section, there occurs one of the junction of the upper 

 and middle Drift, which shews both these formations in strict con- 

 formability to each other, and arching under the influence of lateral 

 pressure, somwhat in the same manner in which the beds are ex- 

 hibited in the section of Aldringham church. 



I am. Sir, etc., Seakles V. Wood, Jtjn. 



FAULTS IN THE DRIFT AT HITCHIN. 

 To the Editor of the GtEoxogical Magazine. 



Dear Sik, — My friend, Mr. A. H. Green, who is nothing, if not 

 critical, has been very gentle in his criticism in my case ; and, 

 iadeed, he is so genial a man that I am sure it must go against 

 his grain, and be an act of stern duty in any case to find fault at all. 

 Perhaps this may be the reason why he overlooked the faults at the 

 Hitchin station. I can hardly think they have grown larger since 

 his visit. But there they are ; and confused as the mass of gravel 

 and loam, which form the Boulder-drifts in that locality, may be, 

 there is a tell-tale bed of conglomerate at the bottom which has 

 betrayed all its movements— while surely, not even a tyro could 

 mistake the dark brown gravel which caps the drift and fills the 

 pipes, and which is so common in the Hitchin section, for the light- 

 coloured sand and loam below. 



The uneven surface of the Chalk here is indeed due to the same 

 cause which has produced so many inequalities in the surface of our 

 island — viz., the much-abused " unequal elevation " of faulted ground, 

 however these faults may have been produced. In the case of the 

 Chalk, that may, no doubt, in some cases be due to sinkings over 

 subterraneous cavities produced by rivers and streams in Post-glacial 

 times. For this idea I am indebted to my friend and former col- 

 league, Mr. Thomas T. Mc K. Hughes, with whom I had previously 

 examined the Boulder-drifts near Hertford, and therefore came to 

 the section more prepared for examination than I should otherwise 

 have been. 



