Geological Society of London. 131 



work in the time of the Romans, but had been exhausted for 400 years. The stone 

 (Lincolnshire limestone) was the building-stone over a large district in ancient times, 

 and its excellence was proved by time. 



The escarpment south of the Nene valley at Wansford presents the same sequence 

 as that of the Stamford Field — Cornbrash to the Upper Lias inclusive. The railway- 

 tunnel is excavated in the Lincolnshii-e limestone. East of this, at Castor and Water 

 Newton, and west of the same point at Elton, the Lincolnshire limestone thins away, 

 and the two estuarine series again come together in vertical contact. Along the 

 Nene valley towards Northampton the southern escarpment presents the complete 

 sequence of beds from the Oxford Clay to the Upper Lias inclusive {minus the Lm- 

 colnshire limestone), as far as Thrapstone. Here the Oxford Clay and Cornbrash 

 part company and trend southward, the other members of the series (Great Oolite Clay 

 and limestone, Upper Estuarine, Lower Estuarine and ferruginous beds of North- 

 ampton sand, and Upper Lias) continuing on to the Northampton district. 



The author contended that the stratigraphical and palEeontological evidence com- 

 bined to establish the position which he assumed in his introduction — that the Great 

 Oolite limestone of Northampton was identical with what he considered was Great 

 Oolite at Stamford, and that the " Lincolnshire limestone" was a distinct formation, 

 and a member of the Inferior Oolite series. 



He had confidence that he had shown that the series of beds in the north-eastern 

 portion of the northern division of Northamptonshire comprised all the beds between 

 the Oxford Clay and Upper Lias inclusive, including the Lincolnshire limestone ; and 

 that those of the south-western portion comprised the same sequence, excluding the 

 Lincolnshire limestone. 



He considered that the Great Oolite Clay represented the Forest Marble and the 

 Bradford Clay of the "West of England ; that the Great Oolite limestone was nearly 

 equivalent to the Great Oolite of Bath and the Cotteswolds, and to the upper beds 

 of Minchinhampton ; that the Upper Estuarine might be nearly identical with the 

 Upper Plant Shale of Yorkshire, but more certainly with the Stonesfield slate of 

 Oxfordshire ; that the Lincolnshire limestone was nearly synchronous with the grey 

 limestone of Yorkshire (Inferior Oolite), and probably with the lower portion of the 

 Am. Humphriesianns zone of the west of England, but extending a little below 

 this zone ; that the Lower Estuarine answered to the Lower Plant Shale of Yorkshire, 

 but had no representative in the west; that the upper portion of the ferYuginous beds 

 of the Northampton Sand was nearly upon the same horizon as the Glaizedale and 

 Dogger beds of Yorkshire and the Am. Murchisonce zone of the west ; and that the 

 lower portion of the Northampton Sand was represented by the Am. opalinus zone 

 and the Midford Sand. 



Discussion. — Mr. Etheridge expressed his obligation to the author for his paper, 

 and for the remarkable collection of fossils he had exhibited. The ground over 

 which he had worked was one the features of which had required a great amount of 

 well-directed labour to decipher. He considered, however, that Mr. Sharp and Mr. 

 Judd had settled the question of the sequence of these rocks, and their relation to the 

 Oolitic beds of Yorkshire to the north, and Gloucestershire to the west. The im- 

 portance of the determination of the position of a bed of such commercial value as the 

 Northampton sands could hardly be over-estimated ; and it was to Mr. Judd and to 

 the author that this determination was due. It had, moreover, been attained under 

 very adverse circumstances ; for at the time when the Survey of the district had been 

 undertaken, the Lincolnshire limestone had not been recognized ; and even Prof; 

 Morris had at first failed to see that this bed intervened between the Northampton 

 sand and the Great Oolite. It was mainly due to the extensive collection formed by 

 Mr. Sharp that the key to the existence of this important bed and of the geological 

 history of the whole district during the Mesozoic period was discovered. The 

 mapping of the country was not to be effected by studying merely its lithological 

 characters, but was mainly dependent on a knowledge of the palaeontological features 

 of each of the successive beds. Mr. Etheridge pointed out the close correspondence 

 between the position of the Northampton beds and those of Yorkshire, with the 

 exception of the absence of the Great Oolite in the latter area. Though the Stones- 

 field slates and the CoUeyweston beds were so similar in lithological character that 

 even the most experienced might take the one for the other ; yet, when the organic 

 contents came to be examined, the difference became evident ; and in Mr. Sharp's 

 paper stratigraphical evidence had been brought to corroborate the palaeontological, 

 and to show conclusively the difference in the horizon of the two beds. 



