82 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Beaconsfield we meet with no deep sections, and the level of the 

 ground does not vary very materially. Between this town and 

 Holtspur Heath the gravel is again found, and worked in several 

 places, but the underlying chalk is not exposed. 



The cutting made to lower the road in descending from these 

 hills to the valley of Loudwater exposes on the top of the hill a 

 fine section of the gravel ; and, as the slope of the hill is not very 

 rapid, we have beneath this level a section continued for some di- 

 stance through the outcrop surface of the chalk below the level 

 of the gravel, in which remnants of the latter are however preserved 

 in pipes ; the upper portion of these and of the chalk, and all thfi 

 overlying gravel, have been removed. There are seven of these iso- 

 lated pipes which can be well made out within a distance of a few 

 hundred yards. They decrease in size as we descend the slope of 

 the hill ; those near the summit are from 20 to 50 feet in dia- 

 meter, but, as they go below the level of the road-cutting, their apices 

 are not visible. Lower down the hill, on the contrary, we find the 

 apices only of some of the deeper pipes. All, however, are confined 

 to a depth of from 50 to 60 feet beneath the level of the gravel on 

 the top of the hill. The sloping surface of the chalk below that 

 depth is free from any traces of pipes. So also is the chalk in all 

 the cuttings in the valley of Loudwater. 



Carrying the line of section over this valley and across the top 

 of the lane up the hill from the Loudwater station, a pipe 12 feet 

 deep and 5 wide occurs. On the summit of the hill at Flackwell 

 we again meet with the gravel in considerable thickness, and in a 

 pit on the heath, where the chalk is worked, a few large gravel- 

 pipes are well exposed. At a short distance further on the ground 

 rises 30 to 40 feet higher, in consequence of an outlier of the sands 

 and mottled clays of the Lower Tertiaries at the spot marked Mount 

 Pleasant on the Ordnance Map. The gravel merely overlaps the edge 

 of this mass, and does not appear again for some miles. 



The feature to be observed therefore along this line of section 

 is the permanence of a high-level gravel on the hills at an elevation 

 of from 100 to 200 feet above the present valleys. "Where this bed 

 is in contact with the chalk, large and numerous gravel-pipes are 

 always found wherever sufficiently deep sections are opened ; and in 

 descending the slopes of the hills all through this district, wherever 

 there is a cutting in the chalk, at points not exceeding usually 50 

 to 60 feet lower than the hill top (though sometimes extending to 

 80 or 90 feet), detached portions of gravel-pipes are constantly met 

 with ; but lower in the valleys than this level the chalk is invariably 

 free from any traces of these pipes. 



Section No. 2. — Starting from where the chalk rises on the river 

 side, between Rochester and Upnor, no sand-pipes are seen in the 

 pit there opened. Rather higher, in a pit N. of Frindsbury Church, 

 I found three small ends of pipes containing portions of the Thanet 

 Sands, the mass of which sets in a few feet higher on the hill ; these 

 detached pipes are here covered by drift. In a pit by the side of 

 the lane leading N. from the high road to Stroud Hill whidmills are 



