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were shown at our last meeting. This stone must evidently have 

 been deposited where found by the same forces and at the same 

 time as the gravel, and the explanation I have given as to the 

 deposition of the plateau gravel would equally apply to such stones 

 as may be found in it. No very violent force of water would be 

 required to move and transport such a stone as this, and the 

 torrential floods that swept over the district at the last submergence 

 of Dorsetshire would have carried about and shifted Sarsen stones 

 as well as gravel. With regard to the power of currents to move 

 boulders, I may refer to the remarkable experiments recorded in 

 Prestwich's Geology,* by which it was proved that a current of 

 water moving at 10 miles per hour could transport spherical blocks 

 of stone weighing five tons, a current of 15 miles per hour could 

 move blocks of 50 tons, and a current of 20 miles per hour blocks 

 of no less than 320 tons ; it being found that the weight of stone 

 movable increased as the sixth power of the rate of the water 

 current. This fact, actually proved by experiment and mathematical 

 deduction, has not, I think, received the attention it deserves by 

 geologists in their attempts to explain the transport of boulders. 



So far, then, as evidence as to ice-action in Dorset can be 

 expected from a study of Sarsens, I fear that we shall not derive 

 much help. That these stones dotted the surface of the land 

 during the glacial period, far more abundantly than now, cannot be 

 doubted. That they may have been caught up, transported, and 

 perhaps broken by floating ice floes and icebergs during partial 

 submergence is highly probable. But the only evidence of this, 

 except in the case of those found where no Tertiary beds formerly 

 existed, would be in striae or ice-markings on their surface, and such 

 markings, so far as my observation goes, are conspicuous by their 

 absence. The presence of these Sarsens is, however, an unexplained 

 difficulty in the face of the ice-sheet theory, by which — had it ever 

 existed in the county — all such stones must have been carried off" 

 the land surface and deposited beyond the Dorset coast line. 



The stones of Stonehenge will probably always remain a 

 mystery, for the place of origin of many of the megaliths is still 

 contested by geologists. But there seems no reason to doubt the 

 probability ot Professor Judd's supposition, that the foreign stones 

 had been carried there by ice, and so were found ready to hand by 

 the builders. This, however, could only be so if they were trans- 

 ported by floating icebergs, which may have found a favourable site 

 for grounding and depositing their debris on the high table-land of 

 Salisbury Plain. Had an ice-sheet swept over the surface, the 

 presence of the Sarsens at least becomes impossible ; they must 

 have been swept clear away from all table-land, as has been 

 observed by Mr. Wright in Southern Greenland and Labrador.! 

 Altogether, Professor Judd's suggestion affords a more reasonable 

 explanation than the fantastic theory which imagined the transport 

 of these blocks from various parts of England to Salisbury Plain 

 by bands of enthusiastic idolators, who, passing by other suitable 



* Vol. i., p. 84. 



f Quoted by Dr. Colley March, p. 81, from Glacial Magazine, ii., 142. 



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