770 ME. E. WILSON ON TKB DTJEHAM SALT-DISTEICT. 



section, and makes no mention of Messrs. Bell's trial-boring, i. e. 

 the particular section upon which the hypothesis of Permian salt 

 in Durham was first based. We must also interpret in a liberal 

 sense the words " the exact geological position " used by Prof. Hull. 

 It would not be correct to assume that the salt-beds of South 

 Durham, of Cheshire, Worcestershire, and the jS'orth of Ireland lie 

 at exactly the same horizon in the Triassic (Keuper) series, or that 

 they were strictly synchronous deposits. As a matter of fact, the 

 beds of rock-salt in Durham lie near the base of the Upper 

 Keuper (/^) and 1700 feet below the topmost Trias (or we will say 

 the Ehaetics, to fix the horizon still more definitely), whereas in 

 Cheshire the salt-beds come high up in the Keuper Marls (/^), 

 whilst in Worcestershire and in Antrim they probably occupy inter- 

 mediate positions. 



I will now state the grounds upon which I conclude that the 

 saliferous rocks of the Tees valley belong, neither wholly to the 

 Permian formation, nor partly to the Permian and partly to the Trias, 

 but wholly and solely to the Triassic series. In the year 1881 1 made 

 a careful examination of the cores of the rocks passed through in 

 Messrs. Bell Brothers' Saltholme trial-boring, including the 150 

 feet or so of strata beneath the thick bed of rock-salt at that point. 

 Prom this inspection I satisfied myself that the rock-salt belonged 

 to the Keuper division of the Trias. The thick series of regularly 

 bedded and fine-grained red and grey sandstones and marls which, 

 in this and the other sections here referred to (see Appendix and 

 Sections facing p. 782), overlie and graduate down into the saliferous 

 marls, and which underlie and appear to graduate up into the gyp- 

 siferous red marls, show the closest resemblances in their general 

 structure and mineral characters to the Keuper " Waterstones " of 

 the Midland counties. 



The development in this district of some 300 or 400 feet of red 

 marls with beds of gypsum and rock-salt, having very much the 

 character of the Upper Keuper " Bed Marls," beneath a considerable 

 series of red sandstones possessing the characters of the "Water- 

 stones," does not, in my opinion, militate against the conclusion that 

 all these rocks belong to the Keuper series, but, on the other hand, 

 tends to bear out the view, which we have independent reasons for 

 adopting, that the " Bed Marls " and the " Waterstones " can only be 

 arbitrarily separated from each other, that they really form portions 

 of the same rock series, and that the same peculiar physical conditions 

 were maintained during their deposition. The lowest beds met with 

 in the Saltholme boring beneath the thick bed of rock-salt (154 

 feet proved), and described by Sir Lowthian BeU as 'Limestone 

 and marls with gypsum and rock-salt,' also appear to me to belong 

 to the Keuper division of the Triassic series. 



The cores of these beds which I now exhibit, and which were 

 kindly given me by Messrs. Bell on visiting their works at Port 

 Clarence, appeared to be fair samples of the 67 feet or so of strata 

 met with near the bottom of their trial-boring, and described in 

 the sections as " Limestone " or " Magnesian Limestone." I should 



