462 PLEISTOCENE DEPOSITS. CHAP. 



These latter, the sarsen stones, are instances which seem strongly 

 to suggest, perhaps to require, the agency of ice ; possibly, indeed 

 probably, not icebergs broken off from glaciers which reached the 

 sea, but shore ice, or frozen masses of earth, such as are believed 

 to be recognised in particular accumulations of drift. If the Vale 

 of the Ock were once a fresh-water lake, discharging through the 

 gorge above Pangbourn, and the climate were ' glacial/ we should 

 have the required conditions for the transport of the blocks near 

 Swindon and at Long Wittenham. If it were a sea-loch com- 

 municating by a frith through the chalk to the broader sea below, 

 the same results might follow. 



But the great mass of drift pebbles in the Cotswold country and 

 in the wide depressed and elevated regions round Oxford, does not 

 on a first view suggest such an origin. Their actual distribution 

 is due to watery movement on the surface where they rest. If 

 icebergs brought these materials they seem to have left no definite 

 trace of their passage. Still less do we perceive the marks of 

 glacial friction on the surfaces where the pebbles rest. Yet the 

 sudden changes of level and nature of materials of these deposits 

 in particular limited and especially high situations red northern 

 drift, flint masses of every shape and various sizes, sometimes with 

 unworn chalk, in separate patches or layers give occasion for the 

 opinion that something of ice action and currents, less continuous 

 than ordinary streams, and less expanded than lake fluctuations or 

 tidal swellings, must be called in to account for these facts. A 

 climate cold enough in winter to suit the warm-coated elephant, or 

 the hardy reindeer and bear, and cover the Cotswolds and Downs 

 with a variable sheet of ice and snow far deeper than we now see, 

 and subject to periodical melting, might account for the main 

 phenomena in the lower grounds. 



' In visiting the Shipston and Evenlode Valleys,' says Mr. Lucy e , 

 ' I was much impressed with the distinct evidence of the action of 

 ice in all its varied forms of berg, land, and sheet; of the vast 

 mantle of frozen snow and ice which, as it appeared to me, must 

 once have lined the tops and sides of the hills, carrying down with 

 it, when the summer thaws set in, the materials upon which it 

 rested/ This is now a prevalent opinion in respect of many valleys 



Proceedings of the Cotteswold Club, 1869. 



