534 13. WILSON ON THE PERMIANS OE 



At Bestwood, for instance, they replace all but 8 or 10 feet of that 

 rock. 



Then follow ordinary Upper Permian marls (e 3 ) with dolomitic 

 sandstones, &c. ; thickness in Hempshill npcast 21 feet. One of 

 these sandstones is literally covered with annelid-tracks. 



These are succeeded by Magnesian Limestone (<r), rising west at a 

 small angle, and forming a dip slope ; when these beds fall west, near 

 Kimberley, their dip also governs that of the ground : 33 feet are 

 exposed in the vertical, at the east end of the tunnel; and this must be 

 near their maximum hereabouts. I call particular attention to the 

 indications this deposit gives of the proximity of land on the south. 

 It is here (i. e. on the Great Northern Railway line) a coarse-grained 

 thin-bedded yellowish and red arenaceous dolomite. Atvarious levels, 

 and sometimes through several feet, it is more or less gritty, and 

 even becomes finely brecciated and conglomeratic. (Similar gritty 

 bands are met with in the new Midland line west of Bulwell, but 

 disappear going north.) There are also partings of higbly micaceous 

 laminated soft sand, running to 3 or 4 inches thick, and often at 

 small intervals apart. Oblique lamination on a small scale often 

 occurs. Generally in connexion with the gritty bands, the rock 

 shows numerous cavities and casts of bivalves (Schizodus and Mybi- 

 lus) difficult to determine with accuracy. 



Further south at Strelley and at Badford Old Engine Houses the 

 dying-out Magnesian Limestone consists of red flagstones, with odd 

 pebbles and red shales. At Wollaton Old Park Farm and at Bobbers 

 Mill (south of Basford) it reposes on the Lower Permian breccia ; 

 and at Bobbers Mill I noticed, while the Leen sewerage works 

 were in progress, that in the course of a couple of hundred yards 

 south from the turnpike gate the thinning-out Magnesian Limestone 

 passes from an ordinary granular dolomite through a fine to a coarse 

 brecciated rock, which seems to show that here, at any rate, we 

 have reached a definite point on the original south margin of the 

 Magnesian-Limestone sea. 



Succeeding with perfect conformity the Magnesian Limestone, 

 comes a series of thin-bedded slate-coloured sandstones and shales (e 1 ). 

 Inclusive of a breccia at their base, they maintain along the Great- 

 rTorthern-Railway section a uniform thickness of 19 to 20 feet, 

 which (as shown at a point on the section) comprise no less than 

 75 different beds J" to 8" thick. Several of the sandstones con- 

 tain a large amount of imperfect plant-remains, woody stems and 

 lignite permeated with iron pyrites; other bands are covered by 

 annelid markings ; and at least one sandstone shows casts of Sehi- 

 zodus. This series represents the Marl Slate of Durham &c. 



These beds, which with the overlying limestone are traversed by 

 numerous vertical joints, become along these, as also along some of 

 the beds, rusted or discoloured light yellow. Supposing the blue 

 colour to be due to finely disseminated carbonaceous matter inter- 

 mixed with the bisulphide of iron, the discoloration is most pro- 

 bably due to the production of the sulphate and its decomposition 

 into the hydrous peroxide, though the same result may have been 



