336 Aburi/. 



Three or four small lateral vallies, containing a similar deposit, 

 and converging to the main valley, add to the impression which 

 almost involuntarily forces itself on the mind, that it must be a 

 stream of rocks, e'en now flowing onward. 



" The lichens growing on the surface give a delicate blue tint to 

 the stones, and when seen by the light of the afternoon's sun, 

 especially towards the close of the summer season, the font ensemble 

 presents a picture of striking and peculiar beauty. 



" The specifiic gravity of Sarsen stone is about 2500 or 1 J times 

 greater than that of water. The weight per cubic foot is 154 lbs 

 The length of the largest stone at Stonehenge is 25 feet. The 

 weight of the largest stone at Avebury (in the cove of the north 

 circle of the temple), being probably the most massive Sarsen in 

 "Wilts, is 62 tons. A larger specimen stood in the same structure 

 a few years since, but is now unhappily destroyed, the weight of 

 which was not less than 90 tons." 



In a subsequent communication to the same paper (June, 1853), 

 Mr. Cunnington says, "Some important information as to the origi- 

 nal stratum from which these masses of rock were derived, has 

 lately been communicated to the Geological Society by Jos. Prest- 

 wich, Esq., F.G.S. Mr. Prestwich is of opinion that they belonged 

 to a series of beds beneath the London Clay, which he proposes to 

 call the 'Woolwich and Reading beds,' and which constitute the 

 second group above the chalk, in the South Eastern districts of 

 England. 



*' The mottled clays adjacent to the chalk at Alum Bay in the 

 Isle of Wight, the sands and mottled clays of Hungcrford, New- 

 bury and Reading and the shelly strata of Woolwich, all belong to 

 this group. In some localities (as at Nettlebed Hill, near Oxford) 

 masses of rock similar to the Sarsen stones of the Wiltshire Downs, 

 may be seen in their original position in the beds of sand : and near 

 Dieppe there is a continuous bed of them a mile in length. 



"In this county, however, not only the Woolwich and Reading 

 beds, but the associated tertiary strata, have mostly been removed 

 by some powerful agency. The only remaining traces of them are 

 to be found in the outliers of sand and clay in the neighbourhood 



