MR. E. WILSON ON THE DFRHAM SALT-DISTRICT. 769 



the Upper Keuper division of the Triassic series. Upon the re- 

 cently published maps the rocks of this lower subdivision (Water- 

 stones) are shown as occupying the larger portion of the low-lying 

 country intervening between the Jurassic uplands of the Cleveland 

 district and the Magnesian Limestone region north of the Tees, 

 without the intervention of any Bunter Sandstone. The limits of 

 the Permian and Triassic areas could not, however, be defined 

 with precision, owing to the thick cloak of superficial deposits, which 

 renders the study of the solid geology of this district so difficult ; 

 thus the boundary between the two had to be indicated by formal 

 lines, and it is stated on the maps as approximate only. 



From the foregoing references, then, it appears that there are three 

 distinct views at present prevailing with regard to the geological 

 age of the saliferous deposits of the Durham district. First, there 

 is the view, originally expressed, I believe, by Sir Andrew Eamsay, 

 that the principal bed of rock-salt belongs to the Keuper, and that the 

 lower beds of rock-salt, marl, limestone, and gypsum belong to the 

 upper portion of the Permian series. This is the view which Mr. 

 Horace Woodward, F.G.S., adopts in the new edition of that work so 

 valuable to all students of British Geology, ' The Geology of England 

 and Wales ' *. Then we have what I should call the more extreme 

 view of Professor Lebour and Mr. C. E. De Ranee, that all the salt- 

 beds and associated strata, " Ked marly sandstones " &c. (No. 4 in 

 Prof. Lebour's classification), belong to the Permian formation, and 

 that the overlying series of Eed Sandstone and marls (No. 5) 

 represent the Lower Trias or Bunter Sandstone. Lastly, there is 

 the view that all the salt-beds and the whole of the saliferous marls, 

 sandstones, and limestones met with in the lower part of the various 

 borings in this salt-field f above the continuous strata of the Magne- 

 sian Limestone, as well as all the overlying red rocks of the Tees- 

 valley district, belong to the Trias, and to the Upper or Keuper 

 division thereof — to the same general series, in fact, as that which 

 contains beds of rock-salt in Cheshire, Worcestershire, and the 

 north of Ireland. This last is the view which the earlier geologists, 

 judging by the limited evidence then available, took of the matter, 

 and is the one which has always appeared the most probable to 

 myself ij;. In addition to the authority of the Geological Survey, 

 which, as the result of careful and detailed investigation on the spot by 

 highly qualified men, must always carry very great weight, I think 

 I am justified in quoting this as the opinion of Professor Hull ; for in 

 the correspondence relating to Sir L. Bell's paper §, the able author of 

 the " Trias and Permian Rocks of the Midland Counties " refers the 

 salt-rock under Middlesborough to the base of the Keuper Red 

 Marls, and says nothing about ' Permian Salt.' It is only fair, 

 however, to say that Prof. Hull refers solely to the Middlesborough 



* ' The Geology of England and Wales,' 2nd ed. 1887, pp. 221, 241. 

 t See p. 772 and Sections facing p. 782, 



+ " The Permian Formation in the North-east of England," * Midland 

 Naturalist,' vol. iv. 1881, p. 188. 

 § Loc. cit. p. 154. 



