238 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 21, 



and in the immediately adjacent districts. It is these beds which form 

 the cliffs atPegwellBay near Ramsgate (see section No. 1, PL XV.). 

 They range inland from this point to Minster, but, although distinctly 

 overlying the chalk, their position relatively to the other members of 

 the *' Lower Tertiaries" is not seen, as no beds higher in the series 

 occur in this district. They are also well developed on the west bank 

 of the Stour at the old Roman station of Richborough, and again on 

 the side of the road in descending from Woodnesborough church to- 

 wards Sandwich. The actual section at the former place, together 

 with its relation to the strata at the latter place, and to the outcrop 

 of the chalk, is shown in section No. 2, PL XV. 



The Thanet Sands extend over nearly the whole of the district 

 included between Sandwich, Canterbury, and the Reculvers, but are 

 frequently overlaid by the middle division of the lower tertiaries, as in 

 the section at Richborough. The higher beds of the lower tertiaries 

 are here also wanting. The relation, however, of the lower divisions 

 to the whole series can be studied in unbroken sequence in the chffs 

 between the Reculvers and Heme Bay, where the several members 

 of the *' Lower London Tertiaries" pass beneath the "London Clay" 

 (see section No. 3, PL XV.). Further, not only is the co-relation of 

 the several groups well exhibited in these districts, but each division 

 has its distinct lithological character and fauna, and they are all under 

 similar marine conditions, whereas, as these beds range westward, the 

 frequent absence of fossils and the close similarity, in many cases, of 

 lithological characters often render it difficult to determine the lines 

 of separation of the different groups, except where the middle divi- 

 sion contains subordinate fluviatile beds. In fact, in assuming that 

 these Thanet Sands of the Reculvers and Richborough are the same 

 as those which underlie the more fluviatile beds of the central group 

 at Upnor and Woolwich (see sections 4 and 5, PL XV.), and repose 

 immediately upon the chalk throughout Kent, Essex, and part of 

 Surrey, — that they are distinct from the sands which alternate with 

 the mottled clays incumbent on the chalk in West Surrey, Hertford- 

 shire, Buckinghamshire, and Berkshire, and that the latter form a 

 separate group, — it must be observed that neither mineral characters 

 nor organic remains alone suffice to determine the question ; for the 

 proofs depend upon general structure and superposition, upon unity 

 in the general design, and upon certain constant characters and con- 

 ditions. 



The following sections which I have given elsewhere*, and for the 

 use of which I am indebted to Mr. Van Voorst, will serve to illustrate 

 the relative position and importance of the several divisions of the 

 " Lower Tertiaries " in their range from east to west. 



These sections are on a vertical scale of 50 feet to 1 inch. 



* " A Geological Inquiry respecting the Water-bearing Strata of the country 

 around Loudon," 1851. 8vo. John Van Voorst, London. 



