510 Notices of Memoirs — Deep Borings in Kent. 



He describes the drifts of the western part of North Wales, grouping 

 them under two heads : — 



1. The Older or Arenig Drift, or that in which boulders were trans- 

 ported from Arenig into the Vale of Clwyd ; and 



2. The Newer or Clwydian Drift, or that due to the destruction of 

 the older glacial deposits by marine action, during which boulders 

 were carried on floating ice from the north, and flints travelled in the 

 shingle round the coast. All the shells found in it are of species still 

 living on the adjoining coast : but some of the shells found in what 

 he considers part of the same series of deposits in neighbouring districts 

 are of a more arctic type, and may beleng to an earlier part of the 

 same epoch. 



He then gives an account of the principal caves explored about the 

 Vale of Clwyd, and explains their relation in each case to the drifts of 

 the district ; inferring that, while some of them may be older than 

 the marine Clwydian drift, and some may possibly be even preglacial, 

 yet that none of the bone-deposits so far found in any of them can be 

 referred to so early a date. 



XI. — Supplementary Note on Two Deep Boeings in Kent. By 

 W. Whitakek, B.A., F.G.S., Assoc.Inst.C.E. 



THE paper "On Deep Borings at Chatham," communicated in 

 abstract to the last meeting of the Association, was afterwards 

 read, with various additions, to the Geological Society. Since then, 

 however, further information has been got, some of which is of im- 

 portance, especially in view of the fact that the South Eastern Bailway 

 Company is about to make a deep trial-boring at Dover. 



The boring at Chattenden Barracks, near Chatham, has been finished, 

 being taken to a depth of over 1160 feet, the bottom of the Gault being 

 reached at 1162 feet, where sand (Lower Greensand) was found and 

 water got. In my account of the section it was left, in Gault, at 1103 

 feet, and I ventured to say that "some 60 feet more would reach the 

 bottom of that formation " ; this happened in 59 feet. I did not 

 venture, however, to predict the finding of Lower Greensand, as, from 

 the thinness of that series at Chatham, a little southward, it was quite 

 possible that it might soon disappear northward. 



The almost exact correspondence of the combined thickness of Chalk 

 and Gault here, 872 feet, with the same total at Chatham (875 and 

 878 feet in two borings) is noteworthy. Of course there is no "Upper 

 Greensand, which formation is absent at the outcrop on the south. 



The Dover boring has been carried a few feet deeper and abandoned. 

 I have visited the site, and procured a good set of specimens of the 

 bottom clays, of which we had but a few small pieces before. 



These specimens have been carefully examined, and the result of 

 this examination is, I think, worthy of notice. As regards fossils it is 

 simply negative, my colleagues, Mr. G. Sharman and Mr. E. T. Newton, 

 after washing and sifting pieces of many specimens, were unable to 

 detect any organism, with a solitary exception, and that was a simple 

 example of a species of Rotalia, which, struggling into existence 

 in Silurian times, has managed to survive to the present day ! I 

 have some doubts, too, whether this one fossil may not have fallen 



