ON AN ANCIENT SEA-BEACH. 331 



largest, being a boulder of basalt measuring 12 in. X 5 x 3, and another 

 of porphj'rite 7 in. X 4 x 3. The proportion of these stones evidently 

 varies in different parts of the beach, being very low indeed close to the 

 clifF-foot, but rising higher as we work outwards and downwards. No- 

 where, however, have we found them to form more than a very fractional 

 percentage of the whole. 



The most plentiful rock among these strangers is a brown or black 

 laminated bituminous shale, with obscure traces of plants and other 

 fossils. This shale is very light, and when perfectly dry will float, so 

 that it may have drifted along the coast into its present position. Its 

 origin is doubtful, but it is not unlike some of the shales in the estuarine 

 Oolites of the Scai'borough district. Other pebbles are of basalt, granite, 

 quartz of various colours, porphyrite, &c., the whole forming an assem- 

 blage not strikingly different from that of our Glacial beds. Some of 

 these pebbles ai'e well rounded, but others do not seem to have been 

 rolling long on the beach and are almost subangular. The presence of 

 these pebbles is a fact of much importance, since we shall be able to show 

 that the Cliff-beds underlie the oldest boulder clay known in Yorkshire, 

 and these pebbles are the first indications we have had of the existence 

 of glacial conditions in still earlier times. It is evident, however, that 

 they have not been derived from the sub-aerial waste of any Glacial 

 beds capping the old cliff, for in that case we should have found them 

 plentifully in the rain- wash from the clifi" presently to be described ; nor 

 are they, in the opinion of the writer, present in sufficient numbers to 

 indicate the waste of pre-existing Glacial beds anywhere in the immediate 

 neighbourhood, though they may have come from the denudation of such 

 beds at a distance. 



Here and there among the gravel and stones of the beach occur the 

 bones of mammals, birds, and fish, and, still more rarely, shells of the 

 periwinkle, oyster, and other molluscs. These remains are nearly always 

 in a bad state of preservation, being often crushed into small fragments 

 (as are also many of the chalk pebbles) by the settling of the beds, perhaps 

 under the weight of the ice in the extreme Glacial period ; and they are, 

 besides, so softened by the percolating waters that when first found they 

 may often be rubbed into a paste between the finger and thumb. When ex- 

 posed to the air, however, they harden, and occasionally when a bone has 

 lain close under the sheltering cliff", or between the larger stones of the 

 beach, the pressure has been so far removed that they may be got out in 

 fair condition, and then, when gelatinised and repaired, they make good 

 museum specimens. 



The thickness of this beach close to the old cliff is from 3 to 5 feet, 

 but it thickens as we pass down the ledges of the chalk floor on which it 

 rests, so that at the outer edge of our trench, 30 feet from the cliff, it 

 was over 7 feet thick, and in a section we cut further south, where we 

 struck the beds still further from the cliff face, we passed through 9 feet 

 of beach-shingle and sand before reaching the solid chalk. As it 

 thickens it becomes more sandy, so that, though close to the cliff it 

 consists of nothing but loose stones, in passing outwards and downwards 

 we find much sand mixed with the stones, while in the above-mentioned 

 cutting thick seams of pure sand are reached. In this respect the 

 old beach is an exact counterpart of the recent beach at this place, 

 in which there is a similar arrangement of rough loose shingle under the 

 cliff-foot, passing outwards into a flat sandy shore. 



