TIUNSACTIOKS OF SECTION C. 649 



11. The Relations of the Middle and Lower Devonian in West Somerset. 

 By W. A. E. UssHEK, F.G.S. 



This paper deals with the relations of the Foreland grits to the Lynton beds 

 and Hangman grits with which they are successively brought into juxtaposition by 

 fault. 



A patch of Lynton beds on the north of the fault at Oare dipping conformably 

 to the subjacent Foreland grits in the vicinity seemed to the author sufficient to 

 prove the position of the Foreland series at the base of the Devonian strata of 

 North Devon according to the generally accepted view; but he found on the east 

 of Luccot Hill, where the Foreland and "Hangman grits were in juxtaposition, it was 

 impossible to fix upon any definite line of demarcation, either by lithological charac- 

 ters or dip ; although beyond a zone of debatable ground the general distinctive 

 characters of each grit series were perfectly apparent. 



This difficulty caused the author to lend a willing ear to a suggestion of Mr. 

 Champernowne that the Foreland and Hangman grits might really be the same 

 series, the appearance of conformable superposition of Lynton upon Foreland beds 

 at Oare being ascribed to inversion. According to this view the downthrow of the 

 fault at Oare would be to the north. 



The object of the paper is to discuss the evidence in favour of and against this 

 suggestion, its important bearing on the mapping of the area entitling it to this 

 consideration. 



The author advances five points in favour of the hypothesis ; the relative merits 

 of these he then discusses briefly seriatim, and points out three considerations 

 adverse to the hypothesis, and some reasons why such difficulties as are experienced 

 in drawing boundaries between the Foreland grits and Hangman beds might 

 reasonably be expected to occur. He considers the arguments against the hypo- 

 thesis of the identity of the Foreland and Hangman groups, more especially those 

 derived from the typical characters and mode of succession of the rocks composing 

 each group, to be too strong to be entertained without positive evidence in its 

 favour. The author then briefly disposes of the possibility of the absence of the 

 Lynton beds east of Luccot Hill being due to unconformable overlap of Hangman 

 upon Foreland rocks, pointing out that if such were the case conglomerates ought 

 to be found in the Hangman series, and the j unction should also be marked by dis- 

 cordant relations of dip and strike. 



12. Supplementary Note on Two Deep Borings in Kent. 

 By W. Whitakee, B.A., F.G.S. , Assoc.Inst.G.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 importance, especially in view of the fact that the South 

 Eastern Railway 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 1,160 feet, the bottom of the Gault being reached at 

 1,162 feet, where sand (Lower Greensand) was found and water got. In my 

 account of the section it was left, in Gault, at 1,103 feet, and I ventured to say 

 that ' some 60 feet more would reach the bottom of that formation ' : this happened 

 in 59 feet. 1 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. 



