40G PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 24, 



our section passes between these two places, and at a point, therefore, 

 where we may estimate the London Clay to be about 320 feet deep *. 

 A rough measurement by the aneroid barometer gave me 160 feet 

 as the height of the ground at Minster Church (where a Naidilns 

 was found at a depth of 1 6 feet, which shows the London Clay to rise 

 to the surface, a bed of gravel excepted), and 180 feet as the height 

 of the hill at " The Chequers," the highest point in the Island. 

 Between these two places a thick bed of light yellow sand sets in, and 

 attains, with the overlying gravel, a thickness of 20 to 30 feet. 

 This bed, which possibly belongs to the lower part of the Lower 

 Bagshot sands, does not extend much further f. As our section now 

 runs parallel with the shore, we may take the dip of the strata along 

 this part of the line from that of the beds in the corresponding 

 portion of the cliffs, or as nearly level along their strike west and 

 east for a distance of about two miles ; further on, the strata rise 

 slightly eastward. Passing over the bare London Clay' at the east 

 end of the Island, and crossing the entrance of the Swale, we reach 

 Heme Bay, where the London Clay still continues to rise eastward, 

 at an inclination which, about 1|- mile beyond this town, brings up 

 the Lower Tertiary sands to the sea level. It would appear, there- 

 fore, that the centre of the Isle of Sheppey, from Minster to East 

 Church, lies in the deepest part of the curve formed by this line of 

 section ; and, after deducting 30 feet for gravel and sand, it would 

 seem that the thickness of the London Clay is here about 470 to 

 480 feet. 



We vrill now take a line of section (fig. 4, p. 405), intersecting 

 the former one in the centre of Sheppey, and prolonged in one direc- 

 tion south-east to Canterbury, and in the other north-west, crossing 

 the Thames to the clifFs at Southend, and thence to the neighbourhood 

 of Rayleigh. On this line we have a well-section on Blean Hill, 

 where the chalk has been reached at a depth of 160 feet. At 

 Graveney we find the Thanet sands at the surface. The London 

 Clay sets in in the adjoining marshes ; and at Harty, on the opposite 

 shore of Sheppey, attains a depth of 133 feet. Thence, crossing 

 the former line of section (fig. 3, p. 405), near East Church, this line 

 reaches the shore at East End, the dip continuing apparently 

 without much diminution as far as this point J. The cliif between 

 East End and Ramsley, like the hill to the east of Minster, also 

 exhibits, at its highest points, sections of the sands which I refer 



* The curve giving this depth is determined by taking the London Clay at its 

 known outcrop, near Sittingbourne, again at King's Ferrj% where it has been 

 ascertained to be 200 feet deep, and continuing this line direct through Queens- 

 borough and Sheerness. 



t In 1847, I noticed the extension of the Bagshot sands over the top of 

 Langdon-hill to the hills at Rayleigh near Soutliend, and therefore nearly oppo- 

 site Sheppey. They are more important at the former than at the latter place, 

 attaining near Rayleigh and above Benfleet a thickness of 30 to 40 feet. I have 

 not been able to find any fossils in these sands. It is therefore possible that they 

 may belong to some drift bed, but the probabilities are, however, in favour of tlieir 

 belonging to the Bagshot series. 



± In the bed of the Thames I have marked the probable prolongation of the 

 slight anticlinal formed by the chalk at Cliff, Gravesend, and Purfleet. 



