ON AN ANCIENT SEA-BEACH. 333 



the top of the old cliff, and has no doubt once extended over its brow 

 but is now cut off there by the chalky rubble at the base of the drifts. It 

 18 quite 25 feet thick in one part of our excavation, and seems to thicken 

 as the cliff recedes inland. It frequently exhibits fine cross-beddino-. 

 The upper 15 feet seems to be quite unfossiliferous ; but lower down, at 

 about tbe level of the rain-wash, we found a few bones, these being 

 usually far better preserved than those found in the other beds. We 

 have already referred to the anxiety which this sand caused us from its 

 tendency to suddenly collapse and slide in on us ; this happened even on 

 a long low slope. It has evidently been accumulated under the shelter of 

 the cliffs by the wind, and the cliff-face behind it has been beautifully 

 smoothed and rounded by the drifting of its wind-driven particles. The 

 same feature is seen on the cliff-face behind the rain-Avash, but stops 

 short at the old beach where the weathering takes a different form. This 

 rounded surface is quite characteristic of the old cliff, and, as already 

 mentioned, is in marked contrast with the adjoining recent cliff, whose 

 outline is splintered and angular through the action of the winter frosts. 

 This feature points to a long-continued prevalence of strong winds from 

 the south or south-east, nnaccompanied by frost, that have driven up the 

 sand from a wide sandy shore lying to the southward, so as to form great 

 dunes overtopping the cliff. 



The Fossils.— A list of the species that have been identified from 

 among the fossils found in the Cliff-beds is given on the opposite page 

 We are indebted to Messrs. E. T. Jfewton, C. Keid, and H. M. Platnauer 

 for the determinations. 



The asterisks in the columns denote in which bed the fossil was 

 found. 



In the old beach the bones are generally water-worn and rounded, 

 and also often in the rain-wash ; but in the blown-sand they are frequently 

 quite unworn, and in a few instances have their finer angles and delicate 

 muscular markings beautifully preserved. 



Careful search was made for any evidence of man's presence, but with 

 negative results, for among the large number of flints examined none 

 showed any certain signs of having been worked. 



The Olacial Deposits, and their Relation to the Cliff-beds.— We have 

 accounted for about 40 feet of the recent cliff at Sewerby. The remain- 

 ing 35 feet consists of Glacial beds, which it will now be necessary to 

 describe. 



The ChalJc-ruhlle.—At the base of the drifts, resting directly on the 

 chalk on the old cliff, we find a variable thickness of chalk-rubble or 

 gravel, made up of angular and sub-angular fragments of chalk, generally 

 of small size, often partially cemented together by a clayey matrix. This 

 bed is found at the base of the drifts nearly everywhere on Flambro' Head 

 and overlaps the solid chalk, passing down on the north side at Speeton 

 lor some distance over the Speeton Clays. Small drift-pebbles may occa- 

 sionally be found m it, but these are rare. In appearance it is such a 

 bed as might result from the sub-aerial wash, and weathering of the chalk 

 and this origin is generally assigned to it. But whatever the mode of 

 Its accumulation, its connection with the overlying Glacial beds is very 

 close. JNo organic remains have yet been found in it. 

 ^A \'^^ section this chalk-rubble is seen to pass off from the top of tbe 

 old cliff and to continue over the blown-sands with very little immediate 

 change of level. Before leaving the chalk it is about one foot thick, though 



