28-i Bejiorts and Proceedings — Geological Socety of Glasgow. 



of those first formed became extinct, and were subsequently buried 

 under tlie spreading layers of the more powerful cones, which con- 

 tinued in action until the structure was brought to a close, apparently 

 through the gradual decrease and final cessation of the gases gene- 

 rated, the cones ending on the surface of the bed in a series of small 

 minor cones, placed within the circumference of the broad upturned 

 ends of the larger cones. 3rd. That there exists between successive 

 calcareous layers of the cones a film of clay of varying thicknesses, 

 which does not seem to have been noticed nor described by previous 

 observers, and that to this thin layer of clay it is due that many of 

 the cone layers now readily separate from each other when the cones 

 are fractured vertically to their axes of growth ; also, that there is 

 seen to exist within each cone a central axis or tube, now filled with 

 argillaceous sediment, and into which tube all the separating films 

 of clay converge downwards, being there united to the tube. 

 Through the line of this central axis or tube the calcareous layers of 

 the cones were erupted, the separating films of clay being deposited 

 within the cones from the water in which the stratum was being 

 formed. 4th. That the transverse wrinkling seen on the inner 

 surface of the calcareous layers of the cones appears to be due to a 

 creeping downwards of the plastic sediment of each layer, through 

 gravitation, along the slope of the cones ; and, as exemplified ia 

 many other plastic substances moving down slopes, their surfaces 

 are often likewise seen to be dragged into a series of transverse 

 corrugations, owing to the surface film of their layers hardening 

 more quickly than that immediately below. In the cones the 

 wrinkling is at right angles to the line of movement of the sedi- 

 ment ; and it is clearly evident that this was effected during the 

 formation of their several layers. Had the corrugations been caused 

 at any after period by pressure or any other agency, we should 

 naturally expect to find the separating lines of clay also corrugated ; 

 but such is not the case. It is only the upper surfaces of the 

 calcareous layers which are wrinkled, and it is clearly evident that, 

 as the successive films of clay were in every instance deposited on 

 an already wrinkled surface of the calcareous layer, this peculiar 

 character was not of subsequent production. 5th. That the apices 

 of the cones, large and small, are invariably directed downwards iu 

 the stratum, their bases or broad ends being upwards, vertical trans- 

 parent sections of the cones show that there is no truth in the state- 

 ment made by some observers of " cone-in-cone " that the apices 

 are turned inwards towards each other, with their bases directed 

 to the lower and upper parts of the bed. The whole of the evidence 

 afforded by Scottish specimens clearly shows that the action which 

 went to the formation of this curious structure was exerted from 

 beneath upwards and never downwards, and that towards the close 

 of the growth of the structure the ebullition of gas from below became 

 so feeble as to be unable to do more than to form a group of very 

 small cones at the surface of the stratum, and that small quantities 

 of calcareous sediment were then erupted, layer by layer, until their 

 summits became raised above the general surface level of the bed, 



