768 MR. E. WILSON ON THE DTJEHAM SALT-DISTRICT. 



The above classification of Professor Lebour's has been criticized 

 by Professor Green, in ' Nature ' *, on general grounds regarding the 

 impracticability of making precise correlations of the minor divisions 

 of a formation in dissociated areas, especially in the case of " a group 

 of rocks like the Permian, formed in so many distinct basins and 

 under changing conditions, the order and nature of which were 

 probably never the same in any two basins." With the general 

 tendency of these objections I coincide. To arrive at correct con- 

 clusions regarding the classification of the Permian (and the Triassic) 

 rocks of the Durham district, we must compare these rocks with those 

 of the same series in other portions of the same great North-eastern 

 area or ba'^in, with which they are in direct physical continuity, 

 and of which they form a part. All attempts to correlate the Per- 

 mian rocks of Cumberland and Lancashire with those of Durham, 

 Yorkshire, &c., are, I believe, doomed to failure, because these two 

 areas were physically disconnected in Permian times, and on that 

 account the sequence of the possibly synchronous deposits in them 

 is entirely different t. Still more hazardous would it be to attempt 

 to correlate in minute detail, especially in the absence of any 

 strongly confirmatory palseontological evidence, the minor divisions 

 of the Magnesian Limestone of Durham with the rocks of the 

 same series in the equally disconnected and far more distant conti- 

 nental areas. But that it is possible to compare the Permian (and 

 the Trias) of Durham, in their subdivisions, with the same rock- 

 series in other parts of the North-eastern basin 1 cannot doubt ; and 

 it would be a lame conclusion, I consider, to fall back on some 

 general term, such as "Poikilitic" or " New Red Sandstone," for 

 the united Permian and Trias of Durham, because the characters 

 and succession of those rocks in that district are not precisely identical 

 with what we find them to be further to the south. 



Sir Lowthian Bell, in his essay " On the Manufacture of Salt near 

 Middlesborough," does not himself consider the question of the 

 geological age of the saliferous rocks of the district ; but in the 

 discussion which followed the reading of his paper several diverse 

 opinions on this head were expressed by some eminent authorities. 

 Sir W. W. Smyth said, " It had been already shown pretty clearly 

 that the formation in which the salt was found was of a different 

 period, and of a different quality to that of the Cheshire salt-beds." 

 On the other hand. Professor Hull wrote that " The salt-rock under 

 Middlesbrough seemed to occupy the exact geological position of 

 that in Cheshire, Staffordshire, Warwickshire, and at Carrickfergus, 

 near Belfast, being at the base of the New Red Marl (Keuper 

 division of the Trias), and above the New Red Sandstone (Bunter) ; " 

 whilst Mr. Bauerman observed that the subject of the paper was 

 " very interesting, but, like many other interesting subjects, obscure." 



The Geological Survey of England class the saliferous beds of 

 South. Durham with the lower or " Waterstones " section (/^) of 



* ' ]S"ature,' vol. xxxvi. 1887, p. 289. 



t "The Age of tlie Pennine Chain," Rep. Brit. Assoc. 1879, p. 343, and 

 Geol. Mag. 1879, p. 500. 



