468 



NA TURE 



[March i6, 1893 



Sandgate itself neither the Atherfield clay nor the Sand- 

 gate beds are well exposed, but on the seashore between 

 there and Folkestone we meet with the white-weathering 

 massive limestone of the Hythe beds at Mill Point, and 

 to the west of it. They are here dipping east at a 

 moderate angle, and if this dip is continued, as the beds 

 rise to the west, there would be room for the 60 feet of 

 them which are seen at Hythe, between their probable 

 outcrop in the lower part of the Enbrook Valley and low- 

 water mark, opposite its debouchure. It must Jse here, 

 if anywhere, that the recorded appearance of Atherfield 

 clay occurs — for the state of things above described must 

 here be terminated by a fault, as will be presently ex- 

 plained, and nowhere else along the coast till Sandgate is 

 entirely passed can this clay occur within 40 yards sea- 

 ward of low-water. On the east side of Enbrook, how- 

 ever, there is no landslip, and the actual landslip is thus 

 shown to have nothing to do with the Atherfield clay. 



Above the strong bands of Hythe limestone, however, 

 west of Mill Point, are seen about 20 feet of soft, crumb- 

 ling clay, occupying the base of the low cliffand becoming 

 sandier above, as described by Mr. Price, and it is easily 

 seen that the bottom of the Enbrook Valley is excavated 

 in clay. The same clay is admirably seen on the other 

 side of Sandgate, in the first cutting beyond Hythe 

 Station on the branch line from Sandling Junction, so 



spring, which may indicate the line of another fault ; or 

 it may be that all this is only a surface slip ; but, in any 

 case, Folkestone beds occupy the actual surface. 



The strike faults thus indicated are only what we might 

 expect if the strata broke, as they so often do, during 

 their upheaval. It is plain that such faults will rather 

 complicate the surface exposure of the clayey rocks which 

 overlie the Hythe limestone. Now, if we allow some 100 

 feet for the Sandgate beds, so as to include in the title all 

 that portion of the series above the clay band at the base, 

 which is not strengthened by the occurrence of indurated 

 bands, and draw, from the purely geological considera- 

 tions detailed above, the boundary of their surface ex- 

 posure, which will not be an entirely simple one, it ex- 

 actly coincides with the boundary of the disturbed area. 

 Thus the upper boundary commences just beyond the 

 town on the west, and runs very nearly along the line of 

 the most westerly fault, till the latter has Folkestone beds 

 on both sides of it ; it then changes direction, and runs 

 parallel to the outcrop of the Hythe beds on the foreshore, 

 sloping down to a point above West Lawn, that is, to the 

 probable position of the second fault ; it is then thrown 

 back along the probable line of that fault. It then again 

 changes its direction and runs at first parallel to the 

 second outcrop of the Hythe limestone, afterwards 

 sloping down rapidly to the shore, so as to follow what 



that though it is not now well exposed in Sandgate itself, we 

 may be sure that it forms a continuous band immediately 

 above the Hythe limestone. 



Now, continuing to examine the coast below Sandgate 

 on the west side of Enbrook we find an outcrop of Hythe 

 limestone nearly opposite Farleigh House. Here also it 

 has a dip towards the east ; but it has also an abnormally 

 high dip — perhaps 10^ — inshore ; such a dip in itself 

 indicates a dislocation in the neighbourhood, but inde- 

 pendently of this, the position of this band at the same 

 level as that at Mill Point, while both bands dip, proves 

 that there is a fault between the two, probably along the 

 Enbrook Valley, with a downthrow on the west. This 

 brings down the clay band at the base of the Sandgate 

 beds to the sea level immediately to the east of the lime- 

 stone above mentioned, and further on, to the east of 

 the coastguard station, the sandy beds of the Folkestone 

 series, which may, however, have slipped. 



Going further west, we find the same band of Hythe 

 limestone exposed on the sloping shore, having a similar 

 easterly dip ; but not so great an inshore dip, which, 

 unless this were a lower band of Hythe limestone 

 (which other observations negative), proves a second fault 

 between these two, with a downthrow also to the west, 

 but of smaller amount. Further west again, and just 

 beyond the town, the sandy Folkestone beds are found at 

 a lower level than they should be if the stratification were 

 regular, and in the slight valley intervening there is a 

 NO. I 22c. VOL. 47] 



would be probably the line ot outcrop of the first hard 

 band in the possibly slipped mass of the Folkestone beds. 

 The conclusion from this seems inevitable. The whole 

 disturbance is due to a motion of soft Sandgate beds 

 where they are unprotected by the overlying hard bands of 

 the Folkestone beds. 



The nature of the motion can be determined by an ex- 

 amination of its upper, and particularly of its lower limit. 

 The greatest amount of visible disturbance has taken 

 place along the upper limit ; here the ground is seen to 

 have slipped downwards and forwards. This might be 

 caused by the collapse of an underground hollow if such 

 a thing were possible, but the loose sandy and clayey 

 nature of the rocks would not admit of such a hollow 

 being formed, and the thick clay band at the base would 

 elfectually shield the Hythe limestones from chemical 

 erosion. The lower limit, however, shows very plainly 

 that the motion has been a simple slip in a south-east or 

 east- south-east direction. In the first place the westerly 

 band of Hythe limestone on the foreshore which abuts 

 against a concrete groin is absolutely unmoved, and the 

 sea-wall above is quite intact (which is a second proof — 

 if, after what has been said above, any further proof were 

 needed, that the Atherfield clay has nothing whatever to 

 do with the matter). In the second place, immediately 

 to the east of this outcrop, the sea-wall has bulged for- 

 ward by about three feet, as shown by the next, wooden, 

 groin, and near low- water mark the overlying clay is seen 



