182 ME. B. SMITH OX THE Vol. lxxiv, 



In the direction of Woodlands and Aston Glebe the pillars occur 

 closer and closer together, and increase in size and irregularity, 

 until they form with the coarsestone a fairly continuous seam with 

 a, nearly unbroken ' cap.' The greater continuity of the gypsum 

 in the seam seems to have permitted of a consistent support to the 

 cover, which therefore held firm. 



The breccia furnishes the following points of interest : — 



(a) The gypsum was formed in situ., as such, and accumulated chiefly 



in stratiform manner at isolated points in pillars, separated by 

 horizontally-bedded marls. 



(b) These pillars may unite and form, in conjunction with a certain 



amount of coarsestone, a continuous bed, as at Aston Glebe. 



(c) The green coloration of both marl and gypsum must be original. 



a fact that should be borne in mind when the subject of colour 

 in variegated strata is under consideration. 



(d) The gypsum appears to have remained in a soft condition while a 



certain thickness of cover was being deposited. 



(e) If the cover collapsed in the manner suggested, the upper white 



gypsum must have been slightly more rigid than the lower red 

 gypsum. 



III. Gypsum Deposits of other Districts. 



If we now review some of the g} T psum deposits of other districts 

 it becomes possible to interpret certain puzzling features in the 

 light of the ChelLaston Breccia. 



That which is true in the case of these nearly isolated pillars on 

 the fringe of the more continuous beds of gypsum must be true 

 also for the beds themselves. We ma3 r , therefore, conclude that the 

 extensive seam of gypsum worked at Aston Glebe, Chellaston, and 

 the similar seams occurring at about the same horizon l at Fauld, 

 Sudbury, Gotham, and Kingston-upon-Soar (where the pillars are 

 termed ' bullets ' and the coarsestone is described as ' fault * ) must 

 Tiave been deposited in their present arrangement on the floor of an 

 enclosed basin. From floor to cap the beds are original deposits, 

 sometimes pure, at other times mixed with sediment. 



Aston Glebe. — At Aston Glebe the seam is fairly continuous, 

 and varies from 1 to 10 feet in thickness, the gypsum often 

 occurring in irregular beds or posts, from 6 inches to 2 or 3 feet 

 thick, sometimes separated by 1 or 2 inches of stratified marl. 

 There are no balls or pillars of uniform size ; but the larger masses 

 of white rock are chiefly found near the top of the seam, the coarser 

 and redder rock occurring below — an arrangement comparable with 

 that in the Chellaston 'pots." Some of the masses of white gypsum 

 weigh hundreds of tons. 



1 Abo\it 140 feet below the base of the Tea-green Marls. This is the lower 

 belt of workable gypsum, belt B. The higher belt (A) of the Newark district 

 comprises about GO feet of strata immediately below the Tea-green Marls. 

 See ' Special Reports on the Minei-al Resources of Great Britain : vol. iii — 

 Gypsum & Anhydrite' Mem. Geol. Surv. 1915, p. 9. 



