62 G. W. Lamplugh — The Yorkshire Boulder-clay. 



I do not propose in this paper to enter into the intricacies of this 

 section further than is necessary to explain the relations of the shelly 

 sand, leaving for some future occasion the discussion of the drifts as 

 a whole. The accompanying section (Fig. 1), as seen in the cliff on 

 the east side of the recess, will give some idea of the character and 

 complexity of these deposits ; and a few words of description will 

 also be necessary. Between this and the opposite side of the hollow 

 there are, however, considerable differences, the west side showing 

 a much greater development of Boulder-clay, and a corresponding 

 diminution in the thickness of the stratified beds which there lie 

 tolerably evenly, and chiefly below the mass of the clay. (See Fig. 1.) 



The Section. 



The chalk-rubble (1) which rests on the chalk in this section 

 differs only slightly from that which forms the base of the drifts 

 nearly everywhere on the headland, but is of unusual thickness, and 

 is distinguished by the presence of well-marked bedding-planes. Its 

 thickness in the middle of the valley may,, however, be more apparent 

 than real, as 1 think it very probable, as suggested above, that we 

 may be looking towards a hidden wall, or very steep slope, of the 

 solid rock against which this rubble is banked. 



The curving and steeply-sloping planes of stratification of this 

 deposit look like cross-bedding, but are not of the normal character. 

 Instead of sloping parallel to one another as in ordinary cross- 

 bedding, most of the bedding planes converge downward, in sweeping 

 curves, upon one horizon. This appearance, again, may possibly be 

 due to the obliquity of the section. 



The manner in which, on the west side of our section, the upper 

 part of this rubble ends up against Boulder-clay, and on the east 

 passes into it, shows that the rubble must in some degree have been 

 formed contemporaneously with the clay. The occasional presence 

 in it, also, of erratic blocks of large size, and the broken character 

 of the chalk surface below it, point to a glacial origin ; but its' 

 bedding and its connection with thick masses of sand and silt (lb) 

 between B and A, show that it can scarcely be considered as true 

 bottom-moraine. 



I may briefly state that I think it has probably accumulated in 

 the hollow between the glacier and the old cliff before the advancing 

 ice had yet over-ridden the chalk ; but to show clearly how this, may 

 have taken place would need a longer disquisition on the general 

 character of the drifts than I propose now to make. 



The lowest Boulder-clay (2) is seen as a tolerably solid mass on 

 the south-east side of our section (Fig. 1), and it is even better 

 developed on the headland immediately to the eastward. But if it 

 be traced in either direction, it loses its massive character and shows 

 a disposition to include irregular and contorted threads, veins or 

 patches of stratified beds (2a). These stratified beds consist of sand, 

 silt, gravel, clay, or even occasionally, though not in the immediate 

 vicinity of this section, of transported Secondaries. These inclusions 

 are of all shapes and sizes, and it is often difficult to define their 



