Geological Society of Glasgow. 283 



IV. — Geological Society of Glasgow. 

 Mr. John Young, F.G.S., on " Cone-in-Cone " Structure. 



March 12, 1885. — The following is an abstract of the paper read ^ 

 by Mr. John Young, F.G.S., on the remarkable and puzzling struc- 

 ture known as " Cone- in-cone," which has not up till this time been 

 satisfactorily accounted for by any geological observer. Mr. Young- 

 stated that this remarkable rock structure is found in certain sedi- 

 mentary strata belonging to various geological formations, and is 

 chiefly comjDosed of lime, clay, and iron. In the Carboniferous 

 rocks of the West of Scotland it is generally known as a thin stratum, 

 or in flat lenticular masses often closely associated with beds of clay- 

 carbonate of iron which, from the contained fossils, give indications 

 of having been deposited, not in the sea, but under shallow lacustrine 

 conditions. "Cone-in -cone " is composed of a series of vertical cones 

 of varying size, arranged in successive conical concentric layers, one 

 within another, the apices being invariably downwards or to the 

 bottom of the stratum, while the bases of the cones or broad ends 

 are upwards, and in the case of the larger examples terminate on the 

 surface of the bed. The first record of the structure which had 

 come under the author's notice was that by the Eev. David Ure, 

 who, in his history of Kutherglen and East Kilbride, 1793, gave a 

 figure and short description, stating that " cone-in-cone " was found 

 at Mauchlanhole Torrance, Kilbride, and was known to the miners 

 as the " Maggyband." There were also several other notices by 

 subsequent observers, and in these the formation of the structure had 

 been ascribed to the action of various causes, such as chemical pre- 

 cipitation, the action of pressure on concretions in process of forming, 

 and to a kind of crystallisation in the stratum after the deposition of 

 the sediment of which the bed was composed. Mr. Young next 

 pointed out in detail how he had been led during the careful study 

 of a large series of specimens of " cone-in-cone," obtained from 

 various localities of the western Scottish coal-field, to form very 

 different conclusions as to the origin of the structure from those 

 previously advanced. In these specimens are revealed external 

 characters and points of internal structure which apparently had not 

 been recorded, or at all events had been overlooked in all the descrip- 

 tions which had come under his notice. Briefly stated, the following 

 are the chief conclusions to which he had been led : — 1st. That 

 '' cone-in-cone " structure is not due to any known chemical precipi- 

 tation of sediment, subsequent pressure on concretions, or to crystal- 

 line action in the stratum after the composing sediment was deposited, 

 but was in all probability formed by the upward escape of gases 

 generated in the deposit whilst the bed was in the process of forma- 

 tion, the gases being derived from the decomposition of the organisms 

 present in the sediment, each ebullition of gas being marked within 

 the cones by a new or successive layer of calcareous sediment. 2nd. 

 That the cone structure originated in the lower portion of the' 

 stratum, the cones at first being small and numerous, but as the bed 

 increased in thickness from the upward growth of the cones, many 

 1 From report in North British Daily Mail, March 14th, 1885. 



