By Professor T. Rupert Jones, P.RS., L.G.S., ge. 187 
action into the deep valleys of Portisham and Bridehead beneath.” 
** Geologist,” vol. xvi., 1863, p. 30. 
Originating 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 shures 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 
