1854.] SORBY ON YEDMANDALE. 333 



Pickering. The configuration of the parts about e shows that the 

 top bed has been partly removed, and a small outlier left at f. 

 From d to c a narrower valley was cut down to a uniform plane 

 of bedding, somewhat lower than north of d. The absolute de- 

 pression at d may be explained by supposing that, in this change 

 of level of the bottom, an eddy was formed, as would indeed almost 

 necessarily be the case ; and the much deeper and larger amphi- 

 theatre, at and below e, was probably due to a similar cause. 

 Though the mean direction of the valley below this is straight, yet 

 it is curved considerably ; but the curves are all situated in parts 

 where, on this supposition, the currents from lateral ravines would 

 have given rise to them. After the valley was excavated, it would 

 appear that the current became less, so that some of the detritus 

 removed from the upper parts could be accumulated in the valley, 

 when the chief part of it would be deposited, in a deltoid form, in the 

 manner and in the places where it is now found. 



The north-north-west line of current is very similar to what must 

 have occurred during the deposition of the northern drift of the 

 neighbourhood ; and there are some reasons for believing them to 

 be related to one another. A few small erratic boulders and pebbles 

 are found on the higher parts of the hills, but no great deposit of 

 drift, which attains its maximum on the low lands towards the sea- 

 coast. In those valleys that are protected from the north, no 

 erratics are found, except just at their lower ends ; but they have 

 been drifted into those opening towards it. This would then lead 

 us to infer that these valleys existed at the period of the Drift. 

 However, as already mentioned, their lower ends have been exca- 

 vated in drift in such a manner as to show that some currents did 

 pass down them afterwards, so that the surface of the sides and 

 bottom of the valley was rendered uniform and continuous with the 

 parts where none was deposited. If such then be the case, it 

 should appear that both previous to and after the deposition of the 

 drift, northern currents passed over the district. In my paper on 

 the contortions in the drift of the Yorkshire coast (Report of the 

 Geol. and Polyt. Soc. of the W. R. of Yorkshire for 1851, p. 220), 

 I have shown what I consider to be evidence of icebergs having 

 been present during the whole period of the Drift, as well as northern 

 currents ; yet not of great intensity, or else one can scarcely suppose 

 that such deposits as it consists of could have been accumulated. 

 Perhaps, therefore, on the whole, the general phsenomena of this 

 locality may be best explained by supposing that at first very con- 

 siderable currents, probably due to movements of elevation, pro- 

 ceeded from some point near to north-north-west, a direction well 

 agreeing with what would be produced by such as have really oc- 

 curred ; that these denuded the district and excavated valleys along 

 lines of weakness ; that afterwards the northern drift was accumu- 

 lated, currents being present that moved in much the same direction, 

 but with very much less intensity, and which subsequently, to a 

 certain extent, denuded and cut valleys in this drift. The whole was 

 then elevated, and the sea, acting at various levels, somewhat modified 

 the surface ; and streams of modern drainage, bemg ultimatelj^ formed, 

 filled up some of the original small lakes, and somewhat altered the 

 configuration of the previously existing valleys. 



