144 Geological Society : — 



for the " porphyroids " of the Ardennes. But in 1882 one of them 

 had visited this region, and was then convinced that the porphyroids, 

 which closely resembled the rock of Sharpley, were felstones which 

 had been rendered schistose by subsequent pressure. The result of 

 their subsequent work in Charnwood has convinced the authors that 

 the rocks of Sharpley and of Peldar Tor are in the main of a like 

 origin and history. The mass of Bardon Hill, where the quarries 

 have been much enlarged, has also been studied, and some details in 

 the section formerly published have been corrected. The schistose 

 bands, on which the authors relied as marking horizons for strati - 

 graphical purposes, prove to be zones of exceptional crush. The 

 occurrence of a rock exactly resembling that of Peldar Tor is fully 

 established. It is extremely difficult to decide upon the true nature 

 of the rocks which are chiefly worked in the pit, but the authors 

 remain of opinion that for most of them a pyroclastic origin is the 

 more probable. 



Some notes are added upon the relations of the noncrystalline 

 igneous and the sedimentary rocks of the Forest, upon the Black- 

 brook group, and upon the fragments and pebbles in certain of the 

 coarser ashy deposits. Some remarks are made upon the glacial 

 phenomena exhibited in the Forest-region ; these indicate that 

 this cannot have been overridden by a great northern ice-sheet, 

 and it does not afford the usual signs of the action of local glaciers. 

 At the same time it has been a centre of dispersion for erratics, 

 especially towards the south and south-west, these being found 

 sometimes more than 20 miles away. Hence, in the opinion of the 

 authors, the erratics have been distributed by floating ice during an 

 epoch of general submergence. Some minor " corrigenda " in the 

 earlier papers are noted, with certain changes in the names of 

 localities, bringing them into harmony with the six-inch map. 



2. " Note on a Contact-Structure in the Syenite of Bradgate 

 Park." By Prof. T. G. Bonney, D.Sc, LL.D., F.R.S., Y.P.G.S. 



The author described a specimen, obtained at Bradgate Park, 

 showing a junction of the syenite and slaty rock of Charnwood. 

 The latter rock is very slightly altered ; the former exhibits a 

 number of grains of felspar and quartz set in a matrix which has 

 now a " trachytic," now a devitrified structure. He traced the 

 former into the " micrographic " structure observed generally in 

 these syenites, and discussed its significance. His study of these 

 structures in this and many other instances led him to infer that 

 they generally indicated that the rock, at a late stage, had con- 

 sisted of a mixture of previously formed crystalline grains and 

 a viscous magma, that the temperature of the mass had been com- 

 paratively low, that it had cooled rather gradually, and that the 

 condition of the magma — i. e. one of very imperfect fluidity — had 

 not permitted of free molecular movements among its constituents. 

 Thus this structure, together with certain others mentioned, might 

 be regarded as indicative of " crystallization under constraint." 



