IxXXviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 19X2^ 



borings in this Triassic and Super-Triassic area, ^'ill show how 

 exceedingly few they are in relation to the large area over which 

 they are scattered. Even so, the amount of information yielded by 

 them is remarkable, Avhen we consider that they have rarely been 

 located according to any definite plan, and when further Tve realise 

 the difficulty that has often been experienced in obtaining and 

 interpreting the evidence which they are capable of affording. 



Of the list of borings considered by the 1901 Commission, 53 did 

 not reach the Palaeozoic rocks at all, but ceased in Mesozoic rocks ; 

 29 reached Palseozoic rocks other than Coal-measures ; and 38 

 reached Coal-measures. This list includes several borings put 

 down near the margins of the exposed coalfields, so it cannot be 

 taken as expressing the average constitution of the outcrop of the 

 Palaeozoic floor. 



The light thrown by these borings on the thickness of Xeozoic 

 cover is interesting. The greatest depths at which Palaeozoic rocks 

 have hitherto been struck is 2000 feet at Scaiie, but the cover was 

 1921 feet thick at Erabourne, 1750 feet thick at Scunthorpe, and 

 1728 feet at South Carr. The greatest thicknesses reached by 

 the borings in known synclines of Mesozoic rock are 2610 feet at 

 Marston and 2100 feet at Chartley, both borings ending in Trias. 

 The sub-AVealden boring at Battle ceased at 1900 feet in Oxford 

 Clay, and the Penshurst boring at 1867 feet in Kimmeridge Clay. 



In the third place, there are the inferences which may be drawn 

 from the application of Godwin-Austen's principle that folding and 

 faulting in newer rocks are often due to the posthumous movement 

 of larger folds or faults in the older and unconformably underlying 

 rocks. In other w^ords, that the buried folds ' show through ' 

 the newer cover imperfectly, like a picture ' seen through a glass 

 darkly.' Godwin-Austen applied this principle only to the major 

 folds ; but Marcel Bertrand was able to show that it is in certain 

 cases a fairly trustworthy guide, even in the case of minor folds 

 and faults. This principle has already frequently proved a most 

 • useful guide to buried structures, and as our knowledge grows it 

 n-ill become of ever increasing value, and may, perhaps, enable 

 Geologists to put out to compound interest each fragment of new 

 knowledge gained as to underground structure. It is known, 

 however, that movement along a given line may be in opposite 

 directions during successive periods, and Mr. Lamplugh's recent 

 study of the structure of the Weald has shown that such is t);e 

 case in that region. During part of Mesozoic times the fold was 

 synclinal in character, but it afterwards became a tectonic anticline; 



