78 



flint, chiefly subangular, a few tertiary pebbles, small pieces of schorl 

 rock, Purbeck marble, and quartz up to two inches. 



It appears to be a low lying drift deposit of pleistocene age 

 derived from the Bagshot gravels on Blackdown (Dorset). — 38. 



The subject of Sarsens must now be considered. Blocks of 

 sandy conglomerate occur in the Reading beds of Hertfordshire. 

 The silica cementing these re-arranged materials was derived from 

 decomposition of the soluble silicates of the felspathic constituents of 

 the glacial drift. This conglomerate, which is n\ feet to 3 feet 

 thick, is interesting as continuous with and merging into loose 

 pebbles and sand. — 39. 



The varying amount of silicious cement in Sarsens is thus 

 accounted for, since it must depend upon the quantity, more or less, 

 or none at all, of any felspathic material brought by glacial agency ; 

 and, if true, it would follow that the silicification of Sarsens is itself a 

 proof that they were covered by glacial drift. 



In a similar bed, at Rickmansworth, in Hertfordshire was 

 found, in 1906, a Sarsen about five feet long and two feet six inches 

 wide. It is evidently water-worn. — 40. 



In the same sandy beds which are 30-40 feet above the level of 

 the present River Gade, were found palaeolithic implements, and the 

 molar of an elephant (E. antiquus). 



In 1862, near Winchester, in digging foundations for a house, 

 Mr. DuBoulay found, 12 feet below the surface, buried in a mixture 

 of stones and chalky loam, the boulder of which I show a photo- 

 graph. It was pronounced to be sand-agate, and therefore is either 

 a quartzite or a compact Sarsen. From its lower surface, which is 

 somewhat flat, it rises to a height of 4 feet. A few inches above 

 its base is a well-defined line, above which the whole of the stone is 

 water-worn and perfectly smooth, presenting a mammillated 

 appearance. There are, as well as the bed in which the boulder 

 was found, neighbouring beds of gravel and clay. — 41. 



The Branksome stone we have all seen. Besides its water- 

 worn surface, some groovings were noticeable along its edge, 

 apparently caused by dynamic pressure. It was buried in a fine 

 sand, and weighed about 10 cwt. I believe it to be a Sarsen. 



Valuable help in the question of a glacial distribution of Sarsens 

 was afforded by Prof. Judd in 1901. His article appeared in 

 " Archaeologia," vol. lviii., and was a study of the constituents of 

 Stonehenge. He shows that the megaliths of this monument were 

 shaped on the spot, and he has examined microscopically the chips 

 of stone that lay in the soil. 



He gives them under nine headings, which may be briefly 

 summarised — 



38- Salter. P.G.A., xv., 279. 

 39 — 1909. Upfield Jones. Geol. Field, p. 18=19. 

 40 — Represented on p. 46 of the Geol. Field. 

 41 — Letter to myself. 



