1866.] WHITAKER LOWER LONDON TERTIAEIES. 413 



Woolwich Series in that paper was in some measure a step back- 

 wards. This was owing to my want of the detailed knowledge of 

 the subject which I have since been enabled to get, and partly to a 

 misunderstanding of Mr. Prestwich's writings, caused by the sense 

 in which he has used the term " basement-bed." This is the right 

 place to correct my statement that in the railway-cutting north of 

 Sittingbourne there w-as " nothing like the usual basement-bed to be 

 seen." I first saw that section during a sharp frost and after snow, 

 when, of course, it was neither easy nor pleasant to make a very care- 

 ful examination, but have since been there under more favoura;ble 

 circumstances, in the company of my colleag-ue Mr. Hughes, who 

 mapped that neighbourhood ; and we then found that the lowermost 

 foot or so of the London Clay was often rather sandy, and contained 

 a few pebbles, some teeth of Lamna, and a little clayey greensand — ■ 

 that is to say, that it had the characters of the basement-bed in 

 Berkshire, &c. The like thing occurs at the cliff-section west of the 

 Reculvers, and at some other places, as Mr. Prestwich has noticed. 



In the neighbourhood of Woolwich, Mr. Prestwich has classed 

 part of the pebble-beds with the Woolwich Series, and part with his 

 basement-bed; but such a division seems to me rather arbitrary, 

 and it would be impossible to map it. I have been led rather to 

 look on the whole as one thing, and to separate the pebble-beds from 

 the Woolwich Series, on which they so often rest unconformably. 



It will be seen therefore that, whilst holding to my opinion that 

 the pebble-beds and the uppermost sands do not belong to the base- 

 ment-bed, I now think (with Mr. Prestwich in great measure) that 

 they do not belong to the Woolwich Series — or, in other words, that 

 they are a separate series, to which, of course, some name must be 

 given. That of " Oldhaven Beds " is a good one, and for two rea- 

 sons, — ^first because they are well shown at " Oldhaven Gap " on the 

 coast west of the E-eculvers, and secondly because it is not an ugly 

 npme — a thing that might perhaps be thought more of in geological 

 nomenclature with some advantage. 



In thus separating these beds from those above and below, I do 

 not really differ so much from Mr. Prestwich as seems to be the case 

 at first sight ; for he classes his " basement-bed" not with the Lon- 

 don Clay or " Upper London Tertiaries," but with the underlying 

 series, to form the " Lower London Tertiaries." Now the term 

 " basement-bed " of a formation means simply a peculiar bed at the 

 bottom of and belonging to that formation ; and, on the other hand, 

 it cannot rightly be used for the bed next helow, in which latter 

 sense this author seems sometimes to use it. The " basement-bed 

 of the London Clay " therefore is the characteristic bed at the bottom 

 of that formation and forming a part of it. 



The difference between my classification and that of Mr. Prest- 

 wich will perhaps be best understood by tabulating the two side by 

 side, as below : — 



