By Professor T. Rupert Jones, F.R.S., F.G.S., Sfc. 137 



action into the deep valleys of Portisham and Bridehead beneath." 

 rt Geologist/' vol. xvi., 1863, p. 30. 



Ori^inatincr as concretions in a bed of sand, the Sarsens had some- 

 what curved outlines, according to a radial arrangement due to the 

 chemical process; and usually one face (the under face) has retained 

 a more marked convexity than the other ; the latter having been 

 subjected to the wear and tear of water and shingle in the earlier 

 time of the denudation of the parent bed, and afterwards possibly 

 to the destructive action of blown sand, when the block lay deserted 

 by the water. Many a further stage, however, of detrition and 

 erosion a vast number of the blocks suffered ; for they remained at 

 levels either continually or occasionally affected by the waves and 

 tide-line of the sea, or on the shores and banks of lakes and rivers, 

 influenced by storms and winter-ice. Hence the fragments of 

 Sarsens, often worn into bizarre forms, and frequently reduced to 

 mere sub-angular stones, in the various gravels of the country ; the 

 smaller remnants being in the later gravels, having been subjected 

 to renewed water-action again and again. " In both sets of gravel 

 (that of the plateaux and that of the valleys) we find numerous 

 Sarsens, or blocks of compact sandstone, derived from the Upper 

 Bagshot Sand. They are broken and water-worn ; but those in the 

 low-level gravel to a much greater extent than those in the higher 

 gravel. The breaking up of these masses .... may have 

 been due to frost rather than to violence; but the surfaces bear 

 evidence of having been slowly worn by sand and pebbles washed 

 over them persistently, worrying out cup-shaped hollows and 

 tunnel-like holes, especially where small trumpet-shaped apertures 

 of the tubes due to congenital root-marks, or the ends of small stems, 

 on fractured faces, presented depressions suitable for the erosive 

 action of eddying sand and water. In some instances a highly glazed 

 surface occurs on the stones, due to the polishing action of blown 

 sand. As this latter operation must take place on a shore or shoal 

 above the water-level, and yet these stones have been imbedded 

 in strata laid down by water, we have here, as elsewhere, indications 

 of a lapse of time, while the several natural operations were taking 

 place, with intermediate oscillations of level, though possibly only 



