1866.] SALTER FAULTS IN DEIPT. 565 



usually interrupt the more general contour of the surface. One of 

 these has been noticed, in the case where the warp has been cut off 

 by a stream. 



When this paper was read before the Society, certain speculations 

 were entered into, in which it was attempted to correlate the above ' 

 sequence of events with those indicated by Mr. CroU as flowing from 

 his theory of climatal changes. It has been thought, however, that 

 these questions had better be reserved for future discussion, and that 

 the paper should appear in the present abbreviated form. 



4. On Faults in the Drift-gravel at Hitchik, Herts. 

 By J. W. Salter, Esq., F.G.S., A.L.S. 



At Hitchin there is an admirable section laid open by the deep cliff- 

 cutting of the Great Northern "Railway, which exhibits faults affecting 

 both chalk and an old gravel which, thanks to the investigations of 

 Mr. Seeley (in Cambridgeshire) and the independent research of 

 Mr. Thomas M'^Kenny Hughes (nearer Hertford), I am enabled to 

 refer to the Boulder-clay period. 



There is no ambiguity in this section. The chalk rises from 

 the railway-level in bold cliffs, 60 or 70 feet high, capped here 

 by chalk- drift, and there by fine, yellowish, stratified gravel — the 

 latter in certain spots, e. g. the hme-kilns, coming down almost to 

 the level of the road, and again rising up to near the top of the cliff. 

 The beds of chalk undulate a good deal ; and the older gravel follows 

 its curves into curious depressed spaces, both north and south of the 

 station. These depressions are, as the section will show, due not to 

 erosion, but to faults*. 



The upper gravel, which fills pipes in the chalk, and everywhere 

 caps both chalk and drift, is much more varied in its composition 

 than the lower and older gravel ; often it is a chalk-rubble, especially 

 along the higher ground, but interstratified with gravelly loam, full of 

 broken and worn chalk-flint. More commonly it is a darker- coloured, 

 yellow, gravelly clay or loam ; and in this latter condition it may be 

 seen in the large deserted gravel-pit just south of the bridge for the 

 high road from Hitchin, south of the station. Close to this bridge is a 

 conspicuous fault in the chalk, which runs across the railway, but is 

 most easily seen on the east side. It runs 30° E. of W. 



Following this southwards, past the opening of the gravel-pit, we 

 again find the chalk in a low cliff- cutting, with numerous vertical 

 fissures, and capped by a conglomerate of rounded flint-pebbles, chalk- 



* The faults in Eoulder-clay, seen in the Ely section, and described by Mr. 

 Harry Seeley (Geol. Mag. vol. ii. No. 18), must not be forgotton, nor his re- 

 mark as to this faulting having taken place previously to the present modification 

 of the country's surface. The downthrow is described as at least 40 feet, and 

 perhaps more. The faults in the Hitchin section have been recognized bj Mr. 

 S. V. Wood, jun., who has drawn them in section No. 6, illustrating his memoir 

 entitled "Eemarks in explanation of the Map of the Upper Tertiaries of the 

 counties of Norfolk, Suffolk, Essex, Middlesex, Hertford, Cambridge, Hunting- 

 don, and Bedford, with parts of those of Buckingham and Lincoln, and accom- 

 panying sections. 1865." 



