148 History of the Sarsens. 
five yards across, and they are often about four feet in thickness, 
Some of them have little basins on their flat surfaces, similar to the 
hollows made on rocks on sea-shores by the gyration of stones set 
in motion by the waves. In the present state of our knowledge 
their distribution seems somewhat capricious. South of Piggle 
Dean they thickly strew the west slope of the valley, the east slope 
being bare. Further up they rise on the east side of the valley on 
Overton Down ; and, ascending the slope, they gradually get smaller 
and more sparingly distributed. In the next valley, near Boughton 
[Wroughton ]Copse, they lie in great profusion, stretching northwards 
towards Toller [Totter] Down, where they are found, but sparingly 
[upon the brick-earth and sand}. On Hackpen they also lie on the 
surface of the same [brick-earth, &c.]. They occur in quantities on 
the Upper Chalk of Marlborough Downs in the valleys east of 
Hackpen, and in the country mapped in the neighbouring sheet [of 
the Geological Map]. On the Chalk Downs north of the Vale of 
Pewsey they strew the surface of many of the valieys in prodigious 
quantities. On the high Downs of the Upper Chalk east and north- 
east of Ogbourn St. Andrew’s, they are comparatively rare. 
West of Marlborough Downs there are few or none on the steep 
flank of Hackpen by the brick-kiln, but they occasionally strew the 
minor valleys that indent the flank of this hill, as for instance, 
where a small stream of stones lies in the bottom of the valley of 
Monkton Down. On the broad plain of the Lower Chalk they are 
scattered on the ground towards Avebury, gradually decreasing in 
number to the west. The huge masses of the temple of Avebury 
were probably transported by the Druids from the adjacent Downs, 
on which they were originally deposited as part of the Tertiary 
strata. The Greywethers lying in places on the Plastic Clay 
[? sands and brick-earth], there is reason to believe that they belong 
to, or else are of a later date than, that formation. In their present 
disjointed state it is also clear that they are only the fragments of a 
stratum which had a very wide range, and which there is every reason 
to believe, along with other Eocene strata, spread over [what are now] 
the Chalk Downs of the West of England. That the Lower Eocene 
strata once extended over broad areas of the Chalk, from which it 
