﻿574 Geological Society : — 



2. ' On the Microscopical Structure of the Derbyshire Car- 

 boniferous Dolerites and Tuffs.' By H. H. Arnold-Bemrose, Esq., 

 M.A., E.G.S. 



The paper deals with the petrography of the Toadstones or 

 igneous rocks of Derbyshire. Brief reference is made to the work 

 of previous petrographers, the age of the rocks, and the question as 

 to the number of beds. The outcrops mapped by the Geological 

 Survey, and several additional ones, have been examined, and the 

 results given in a table for the purpose of the paper and for future 

 reference. 



The Toad stone is divided into massive rocks or lavas, and f rag- 

 mental rocks or tuffs. The former consist of olivine-dolerite, either 

 with granular or with ophitic augite, and olivine-basalt. The rock 

 is often very fresh, but in some places is altered to a diabase. The 

 principal constituent minerals are described. A pseudomorph of 

 olivine, optically like biotite and somewhat like Iddingsite but 

 differing from it chemically, is fully described. 



The latter portion of the paper deals with the tuffs, which are 

 much more extensive than has been hitherto supposed. Specimens 

 are described, taken from thirteen outcrops. 



3. ' On the Origin of the Permian Breccias of the Midlands, and 

 a Comparison of them with the Upper Carboniferous Glacial 

 Deposits of India and Australia.' By B.. D. Oldham, Esq., F.G.S. 



The author first describes the Permian Breccias of the Midland 

 Counties of England, which he had the opportunity of examining at 

 Eastertide of the present year. He describes the characters of the 

 Breccias, and concludes that they were formed subaerially as gravel- 

 fans by rivers charged with a maximum load of sediment, and 

 therefore incapable of performing any appreciable amount of erosion, 

 An examination of many of the fragments at Abberley and some at 

 Church Hill reveals the presence of scratches, which occur in such 

 a manner that the author believes they existed on the fragments 

 before they were transported, and discusses the evidence for their 

 production by ice or soil-cap movement, deciding in favour of the 

 former. 



A short description of the Upper Carboniferous deposits of India 

 follows, and it is pointed out that they differ markedly from the 

 deposits of Britain. Amongst other things the separation of different 

 pebbles by considerable interspace of matrix, and the bending of 

 stratification-planes round a pebble as though the pebble had 

 dropped from above, is noted, and it is maintained that floating ice 

 alone will account for these pebbles being dropped into the Indian 

 deposits. Finally, it is remarked that the so-called Upper Car- 

 boniferous deposits of India and the Permian deposits of the 

 Midlands of Britain may be practically contemporaneous, as main- 

 tained by the late Mr. H. E. Blanford, indicating a possible 

 simultaneous existence of glaciers in England, India, and Australia. 



