570 Reports and Proceedings — 



2. "On some Eesults of Pressure and of Intrusive Granite in 

 Stratified Palgeozoic Eocks near Morlaix, in Brittany." By Prof. 

 T. G. Bonney, D.Sc, LL.D., F.E.S., F.G.S. 



The author briefly described the banded Palaeozoic slates in the 

 neighbourhood of Morlaix, and gave a general account of their 

 microscopic structure. They are greatly contorted and folded, and 

 have evidently undergone very severe pressure. The result of this, 

 as it appears to him, has been the development of minute scales of a 

 light-coloured mica, especially in the darker (originally argillaceous 

 bands) and certain corresponding changes in the more quartzose 

 layers. The cleavage-planes often cut the surfaces of bedding and 

 of this micro-foliation, which are parallel, at high angles, and so are 

 of the nature of " Ausiveichungsclivage.'' 



In certain places these banded slates, after they have attained the 

 aforesaid condition, have been affected by intrusive granites. The 

 result has been the intensifi.cation of the changes which were already 

 incipient. The quartz granules have been doubled in size, the flakes 

 of mica have become four or five times as large, the black material 

 of the argillaceous bands has been gathered into larger granules, 

 and seemingly reduced in quantity (probably by partial oxidation 

 of the carbon), and in some cases andalusite crystals or grains of 

 considerable size have been developed. The rock has become com- 

 paratively hard, instead of friable, and the cleavage-planes are 

 "soldered up" by the development of mica along them. In its 

 general aspect one of these banded rocks (where free from anda- 

 lusite) bears considerable resemblance, macroscopic and even micro- 

 scopic, to one of the less coarsely crystalline, distinctly banded 

 mica-schists, supposed by many to occupy a rather high position in 

 the Archasan series. 



3. " On the Position of the Obermittweida Conglomerate." By 

 Prof. T. McK. Hughes, M.A., F.G.S. 



The author gave an account of a visit to the section at Ober- 

 mittweida, 50 miles S.W. of Dresden, where there is an apparent 

 intercalation of conglomerate and sandstone in a gneissic series. 

 West of the stream at Obermittweida there is seen a crushed but not 

 much altered conglomerate ol felsite and other pebbles, above which 

 gneiss and mica-schist rest, apparently in true sequence numerically. 

 Below the conglomerate no rocks were seen, but at a little distance 

 to the eastward coarse flaked muscovite-scliisfs and gneissic rocks 

 were exposed, apparently underlying it. By a diagram the author 

 showed how the conglomerate might belong to much newer beds 

 caught in a synclinal fold of the schists, and he advanced various 

 arguments in support of this explanation. 



4 " On the Obermittweida Conglomerate : its Composition and 

 Alteration." By Prof. T. G. Bonney, D.Sc, LL.D., P.K.S., F.G.S. 



The author is indebted to Professor Hughes for the opportunity 

 of examining a fine series of specimens of this rock, collected by the 

 latter. The pebbles vary from well-rounded to subangular, some 

 of the smaller fragments occasionally being practically unworn. 

 The matrix is sometimes granular to the unaided eye, sometimes 



