Geological Society of London, 275 



II.— May 11th, 1892.— W. H. Hudleston, Esq., MA., F.R.S.,— 

 President, in the Chair. — The following communications were read : 



1. "On the so-called Gneiss of Carboniferous age at Guttannen 

 (Canton Berne, Switzerland)," By Prof. T. G. Bonney, D.Sc, 

 LL.D., F.R.S., V.P.G.S. 



It is stated by Dr. Heim (Quarterly Journal, vol. xlvi. p. 237) 

 that the stems of Calamites have been found at Guttannen in a 

 variet}'^ of gneiss, i.e. in one of a group of rocks which exactly 

 " resemble true crystalline schists in mode of occurrence. Petro- 

 graphically they are related to them by passage rocks ; at least the 

 line of separation is not easily distinguished. . . . The Palaeozoic 

 formations mostly show an intimate tectonic relation to the crystal- 

 line schists, and have been converted petrographically into crystal- 

 line schists." 



The author describes the result of a visit to the section at Gut- 

 tannen in company with Mr. J. Eccles, F.G.S. (to whom he is 

 greatly indebted for kind assistance), and of his subsequent study of 

 the specimens then collected. The belt of sericitic " phyllites and 

 gneisses,"presumably of Carboniferous age, represented on the Swiss 

 geological map (Blatt xiii.) as infolded, at and above Guttannen, in 

 true crystalline gneissoid rocks, is found on examination to consist 

 partly of true gneisses, partly of detrital rocks. The boulder from 

 which the stems in the Berne Museum were obtained belongs to the 

 latter. These rocks sometimes present macroscopically, and occa- 

 sionally even microscopically, considerable resemblance to true 

 gneisses, but this proves on careful examination to be illusory. 

 They are, like the Torridon Sandstone of Scotland, or the Gres 

 feldspathique of Normandy, composed of a detritus of granitoid or 

 gneissoid rock, which sometimes forms a mosiac resembling the 

 original rock, and which has been generally more or less affected by 

 subsequent pressure and the usual secondary mineral changes. Thus, 

 if the term be employed in the ordinary sense, they are no more 

 gneisses than the rocks of Carboniferous age at Vernayaz (Canton 

 Valais) are mica-schists, but in some cases the imitation is unusually 

 good, and, so far as the author saw, there are at Guttannen neither 

 conglomerates nor slates to betray the imposition, as happens at the 

 other locality. 



2. " On the Lithophyses in the Obsidian of the Eoche Eosse, 

 Lipari." By Prof. -Grenville A. J. Cole, F.G.S., and Gerard 

 W. Butler, Esq., B.A., F.G.S. 



The rock described in this paper differs in no essential particular 

 from that at Forgia Vecchia, or from the obsidian on the north flank 

 of Vulcano ; but the specimens show in a specially striking manner 

 the passage through various stages of lithophysal structure, from 

 indisputable steam-vesicles with glassy walls to typical solid spheru- 

 lites. A full description is given of the formation of spherulites by 

 a double process — firstly, divergent growth from the margins of 

 vesicles outwards, and, secondly, convergent growth inwards from 

 the margins towards the centres of the hollows, until in the smallest 

 cases the fibres from the opposite sides of the vesicle may meet in the 



