184 ME. B. SMITH ON THE [vol. lxxiv, 



the thinner Newark seams) beds the upper portion is usually the 

 purest ; the bottom is commonly coarsestone or foulstone. 



Carlisle District. — In the Vale of Eden, so well known to 

 Groodchild, the deposits of Cocklakes, Acrehead, and Cotehill occur 

 in the gypsiferous shales beneath the St. Bees Sandstone. The 

 seam is as much as 24 feet thick, and is split up usually into 

 three layers, the central being anhydrite. With this exception 

 the seam, as a whole, is very similar to those of the Derbyshire 

 and Staffordshire districts. It is, however, a more continuous 

 deposit and a less stained variety of rock. The lower seam of 

 gypsum is split into two by a bed, or post, of coarse stone of 

 variable thickness. From a purely strati graphical standpoint all the 

 evidence suggests original stratiform deposition. The boundaries 

 (resembling bedding-planes) are as regular as those, for example, 

 in a series of bedded sandstones and shales. The beds forming the 

 floor are parallel to the deposits, and, apart from local disturbance 

 due to solution of the top of the seam, the overlying marls and 

 shales are also regular and undisturbed. The question as to 

 whether there has been any conversion from anhydrite to gypsum, 

 or vice versa, will be discussed later. 



Penrith District. — Farther south deposits of gypsum occur 

 at Kirkby Thore and Temple Sowerby, in the Plant-Bed Series at 

 the top of the Permian deposits. 



At Kirkby Thore Quarry (situated about 1 mile north-east of 

 Kirkby Thore Rail way-Station) the gypsum forms a massive bed, 

 from 18 to 20 feet thick, which is overlain by a gypsiferous ' cap ' 

 and underlain by a gypsiferous 'black post.' The seam shows clear 

 evidence of its formation as a stratified deposit. 



The rock is greenish grey to faintly pink, and of close-grained 

 saccharoidal texture ; but in some cases it consists of selenite- 

 crystals, set in a ground-mass of the finer- textured rock stained by 

 grey colour-bands and splashes which probably owe their character 

 to organic impurity. The bands are narrowly spaced (■§ to £ inch 

 apart), and the seam can be divided into four separate horizons 

 showing different arrangements in descending order (fig. 5, p. 185) : 



(i) Bands nearly horizontal and parallel. 



(ii) Nests of white gypsum set in a dark-grey matrix [' bird's-eye ']. 

 (iii) Bands folded and sometimes contorted. 

 (iv) Bands horizontal. 



Each band of colour is apparently the accompaniment of succes- 

 sive thin sheets of gypsum, similar to some of those in the cap and 

 black post, laid down one upon the other, the contained impurities 

 having been thrust to the surface (or bottom) of each layer during 

 the process of crystallization. They recall the traces of horizontal 

 bedding occasionally visible in the Chellaston pillars. 



In the third horizon the contortions are similar to those which 

 occur in certain other stratified rocks, such as fine sandstones, and 

 were probably due to lateral creep on a gently-sloping floor under 



