572 Correspondence. 



know the locality ; but does it follow that because the river has once 

 flowed at a higher level, therefore the subsequent degradation of the 

 sm-face is the work of the river ? " 



Without discussing Mr. Fisher's views at length, we would beg to 

 call his attention in the present instance to the fact that between the 

 gravel at the 300-feet level and the present river, there exist enor- 

 mous deposits of gravel and brick-earth at all intermediate heights. 

 From this we infer, as we stated in our paper, " that the river deep- 

 ened its bed gTadually, and that since the Medway flowed at the 

 300-feet level, no agents except rain and rivers (and possibly river 

 ice) can have been working at the denudation of the rocks contained 

 within the basin of the Medway" (p. 464). During the time that 

 this was going on, at all events, the valley could not have been ex- 

 cavated by an ice-sheet, although several facts mentioned by us 

 point to the existence of ice, but on a much smaller scale than what 

 is suggested by Mr. Fisher, and with different results. (See pp. 458, 

 465, 469.) Your obedient servants, 



William Topley, Clement Le Neve Fostek, 



Geological Survey Office, Bbeage, neak Helston, Cornwall. 



Nov. 10, 1866. 



ON FAULTS IN THE DllIFT-GRAVEL AT HITCHIN. 

 To the Editor of the Geological Magazine. 



Sir, — In the last number of the Quarterly Journal of the 

 Geological Society there is a paper by Mr. Salter, on some faults in 

 the Drift Gravel at Hitchin, in which the author has expressed him- 

 self I think rather more decidedly than the facts of the case warrant. 



Mr. Salter mentions two sections : The first is seen in a large 

 chalk-pit immediately to the south of the Hitchin Station, and shows 

 Chalk capped by a mixed mass of gravel, sand, clay and brick earth. 

 As far as I could make anything out of this confused mass, the 

 different members seemed to lie in lenticular-shaped beds, and not to 

 have any definite order of super-position ; indeed, I could neither 

 here nor elsewhere in Herts, and Buckinghamshire establish any sub- 

 divisions among the drifts that were of the least value, and came at 

 last to put the whole together under the comprehensive name of 

 Boulder-beds. To retui-n to the section : these Boulder-beds rest on 

 a very uneven surface of Chalk, and my impression was, that the 

 inequalities at the junction had been produced by denudation, or by 

 water percolating through the gravel ; and, though I paid several 

 visits to the spot, I never saw anything that looked to me like a 

 fault. Far be it from me to deny there are faults, but I do think that, 

 if they had been as palpable as Mr. Salter lepresents them to be, 

 they would not have escaped my notice. With regard to the other 

 section, close to a bridge, crossing the railway a little further to the 

 south, 1 dare speak more positively, for I feel almost certain that the 

 gravel here lies in a large pipe in the Chalk. Do the other faults 

 affecting the Drift, of which we hear from time to time, rest on such 

 evidence as this ? I am, Sir, your obedient servant, 



A. H. Green. 

 116, DoDSwoRXH EoAD, Baenslet. Nov. IQth, 1866. 



