99 



may have been transported by ice-floes, in the absence of high 

 ground from which a local glacier could have descended. 



And now, in conclusion, I will revert for a moment to the 

 views of the late Sir Josaph Prestwich in his " Geology "* on the 

 Scandinavian ice-sheet theory, who sums up his account of the 

 glacial period in these words : " The phenomena as a whole go to 

 show that the glaciation of Great Britain was not due to a great 

 Polar ice-cap, but was of local and independent origin." After the 

 first glaciation, he agrees with Mr. Geikie in believing that " a 

 great depression ensued by which Central England, Wales, and 

 Ireland were submerged to the extent of 1,500 to 2,000 feet." 

 Prestwich further adds that he disagrees with the view that the 

 presence of boulder clay containing blocks of Scandinavian rocks, 

 or of striations on rock surfaces in Germany or Norfolk, indicates 

 that the ice-sheet extended there, but that the striations were due 

 to local causes, and the boulders may have been caused by 

 floating ice. Scandinavia was also submerged about 1,000 feet 

 beneath the present sea-level, sea shells being found at heights from 

 200 to 600 feet up. 



I do not pretend that the submergence and floating ice theory, 

 which I have championed in this paper, presents no difficulties, 

 On the contrary, both theories bristle with knotty points, but it 

 seems that they are far more easily solved by the views here 

 advanced than by those who can believe in glaciers, thousands of 

 feet thick, plowing up the ocean bed and depositing fragile shells 

 on mountain tops. A very impartial sketch of the position, giving 

 the views of both parties, and the difficulties and objections 

 advanced by each, will be found in Professor Bonney's " Ice-work 

 in Great Britain,!" to which I have already referred. 



To what conclusion can one come, then, as to the probable 

 condition of Dorset during the glacial period ? A reasonable cor- 

 relation of the facts I have brought forward, supplemented by the 

 valuable observations of Dr. Colley March and some of those he 

 has quoted, will suggest this : that during submergence, floating 

 icebergs and floe ice may have deposited erratics and foreign 

 material, boulder clay, morainic matter, etc., frozen to their bases, 

 in various parts, and possibly where they stranded they may have 

 torn up the soil and scored the tops of hills, but that few of these 

 signs of ice-action have escaped erasion by subsequent denudation 

 — hence the paucity of the evidence now available. That also 

 during the greater part of the glacial period, when Dorset was dry 

 land, it was not covered by any great ice-sheet, but was probably 

 only moderately snow clad, with deeper snow and ice on the hill- 

 tops, forming perhaps in the valleys miniature local glaciers. But 

 from the absence of high collecting ground of sufficient area to 

 supply any great quantity of ice, as well as the comparative 

 shallowness of our valleys, it seems unlikely that such glaciers 

 could have had power to collect or transport much morainic 

 material, even were the temperature as low as in Greenland to-day. 



* Vol. ii., p. 453. 

 t P. 163—200. 



