18 



W. S. Gresley — On " Cone-in- Cone" Structure. 



organic matter in the deposit whilst still in the process of formation 

 and in a soft, sedimentary condition ; each ebullition of gas being 

 marked by a new or successive layer of sediment within each cone." 

 " That the cones, large and small, have their apices invariably directed 

 towards the lower portion of the stratum." 



As, in the coui-se of the last year or two (due chiefly to the occur- 

 rence of some interesting examples of cone-in-cone in the breccias 

 of the Permian ? series in Leicestershire, see Q. J. Gr. S. vol. 

 xli. Proceedings, page 109, and the " Midland Naturalist," vol. ix. 

 No. 97 [new series]), the writer has given some attention to this 

 interesting rock-structure, his observations in the field and elsewhere 

 have brought to his knowledge several important facts, and such as 

 have reluctantly prevented him from accepting Mr. Young's theory. 



Although Mr. Young has gone very fully into the question, he 

 does not appear to have noticed one or two important points often 

 seen in cone-in-cone structure, which I will now endeavour to 

 describe. 



J nat. size. 4 times nat. size. 



(a) In the case of large, strong, well-developed cones, often four 

 or five inches in length (see Fig. 1), and generally composed of com- 

 pact siliceo-ferruginous sandstone in the Coal-measures, which I will 

 call ' master cones ' because they seem to cut out the feebly developed 

 ones in their upward expanding growth ; the walls, or substance of 

 the cones, or conical-shaped cups or portions of such (for whole 

 hollow cones are rarely met with), often as much as a quarter of an 

 inch in thickness between the usual concentric layers of corrugations 

 more or less filled with clayey material, are themselves composed of 

 cone-in-cone formation (also possessing their clay-filled serrations) ; 

 the bases of the cones abutting upwards upon the clay wrinkles 

 which separate each great cone or part of a cone. A reference to 



