426 Reports and Proceedings — 



unable to decide whether these masses are contemporaneous and in- 

 terbedded or intrusive sheets, — both may be present ; but in any 

 case they are older than the granite. He described in some detail 

 the structure of specimens of these altered rocks from many locali- 

 ties, the microscojDic examination of which shows that the pj^rox- 

 enic mineral, whether augite or diallage, has frequently been con- 

 verted into a hornblendic substance, and that actinolite is found 

 filling cavities and fissures in precisely the same manner as other 

 products of alteration. The imperfect cleavage of the more compact 

 varieties is regarded by the author as in accordance with the facts 

 observed in typical slates. The metamorphism of the dolerites is 

 regarded by him as diiferent in kind from that of the slates, and 

 caused rather by a decomposition and rearrangement of mineral 

 substances in situ than by an introduction of new material ; in 

 many cases the process of alteration may be followed step by step ; 

 and from the evidence it would appear that two rocks of similar 

 origin and composition may follow two different lines of metamor- 

 phosis, and thus become converted into two totally diiierent sub- 

 stances ; and again many of the metamorphic rocks have undergone 

 a second series of changes, brought about chiefly by chemical forces, 

 and indicated by the occurrence of micaceous and chloritic pseudo- 

 morphs after tourmaline and an alteration (hydration) of the mica. 



With regard to the origin of the granite of Cornwall, the author 

 said that neither observation in the field nor microscopical study 

 lends any support to the notion that it is a metamorphic rock ; but, 

 on the contrary, that there is the clearest evidence of former deep- 

 seated volcanic action in the disturbance and alteration described in 

 his paper, and in the enormous number of granitic and felsitic dykes 

 intersecting the country for miles. The mode of occurrence of 

 granite in other localities also seems to him to furnish evidence in 

 the same direction. 



14. " On the Eelation of the Upper Carboniferous Strata of Shrop- 

 shire and Denbighshire to Beds usually described as Permian." By 

 D. C. Davies, Esq., F.G.S. 



The author described sections obtained at the Ifton Ehyn Col- 

 lieries and other places in the neighbourhood, and compared these 

 with other sections displayed in different parts of England and the 

 continent, and also in Nova Scotia, and stated his conviction that 

 from the Spfrorizs-limestone upwards to and including the Permian 

 we have one continuous series of deposits. He maintained that there 

 is no real general break in the sequence of the strata or in the con- 

 tinuity of life, but only local unconformabilities marked by equally 

 local gaps in the succession of life. 



15. "Notes on the Physical Geography and Geology of North 

 Gippsland, Victoria." ^y A. W. Howitt, Esq., F.G.S. 



The earliest formation of which any trace is left in this district 

 is the Silurian ; all traces of any older rocks being removed, jfrobably 

 by the same agencies which have contorted and metamorphosed the 

 Silurian slates and sandstones. The surface of all these Silurian 

 strata show signs of great denudation previous to the dei)Osition of 

 the Devonian. The period that elapsed between these two epochs 



