DUIKTS Ol" FLAMBOUOUGII HEAD. 4()5 



with lumps of chalk and some sand, the whole cemented into a very 

 hard mass by the percolation of water charged with lime. The 

 breccia seems to have accumulated in an open joint-fissure of the 

 Chalk, but it is not easy to decide whether the opening of the fissure 

 took place in Glacial times ; whether it is of post-Glacial date and 

 has been afterwards filled in with falling drift fi'om above, as certain 

 other open joints in the neighbourhood have recently been ; or 

 whether it is simply duo to a slip of drift having rested against the 

 clifF-face. But as it is evident that a line of sea-cliffs did exist in 

 this locality prior to the encroachment of the ice-sheet, and as the 

 structure of the escarpment, which is based on clay, must always 

 liavQ favoured the formation of such fissures near its edge, there 

 is nothing improbable in the first supposition. Somewhat similar 

 breccias are of frequent occurrence on the headland (Danes' Dyke, 

 South Sea Landing, Little Thorn wick, &c.), but are usually hori- 

 zontal, and have been formed from gravels lying between the Chalk 

 and the Boulder-clay. 



(s) Speeton (PI. XIII. fig. 13). — Where the Lower-Cretaceous 

 Clays emerge the coast-line abandons the Chalk escarpment and turns 

 northward, thus determining the headland. The surface falls by a 

 steep slope from over 400 to under 200 feet, and on this slope there 

 is evidently very little drift, though the cliff- sections are unfor- 

 tunately very obscure. In these sections, and also in the chalk- 

 pits which have been driven into the face of the escarpment between 

 Speeton and lleighton, we find only a slight depth of red gravelly 

 clay above the Chalk, the slope having probably been too steep for 

 much drift to lodge. 



Some of the great slips of chalk which characterize the vicinity 

 seem to have reached their present position before, or during, Glacial 

 times, and are sometimes overlapped by the Glacial deposits and 

 sometimes confusedly mixed with them. 



Towards the foot of the slope the drifts thicken rapidly, comprising, 

 at the base a rubble of fine subangular fragments of chalk with 

 seams of sand, overlain by dark Basement Boulder-clay with irre- 

 gular stratified beds, and this again by gravel and brown Boulder- 

 clay. The deposits are therefore quite analogous to those on the 

 escarpment, and also to those on the other side of the headland ; 

 and it is remarkable how slightly the character of .the drifts is affected 

 by this great and sudden change of level. Had there been, as has 

 been supposed, a long mild interval between the formation of the 

 different Boulder-clays, the older deposits would scarcely have with- 

 stood erosion and remained on the crest of this steep escarpment. 



In the deep ravine of Speeton Gap, the drifts pass suddenly off 

 the Chalk, on the northern side resting on the Speeton Clay, without 

 any marked alteration of character. Some masses of lied Chalk 

 which occur in the base of the deposits in Black Cliff seem to be 

 included in the Basement Clay, but whether they are transported 

 masses or merely pre-Glacial slips I have not been able to decide. 

 Xear the same place soft sands are found below the chalky rubble. 



