Geological Society of London. 139 



felspar, with viridite and some iron peroxide, full of larger frag- 

 ments of felsj)ar crystals (generally both of orthoclase and plagio- 

 clase) and lapilli. The structure of these is often distinct, some are 

 certainly andesites, others some kind of trachyte ; slaty fragments 

 are also present, and occasional grains of quartz. The authors 

 express their opinion that all the larger felspar crystals, and most, 

 if not all, the quartz grains, are of clastic origin, even in the more 

 highly altered varieties. Some of the larger fragments in the 

 breccias were examined, and referred in part to devitrified trachytes 

 not very rich in silica. The igneous rocks were then described. 

 The syenites of the southern and northern districts were shown 

 probably to, belong to one system of intrusion. The hornblendic 

 granite of the Quornden district was also described, and the micro- 

 scopic structure of the different A'arieties of it and the above inves- 

 tigated. A number of igneous rocks generally forming dykes in 

 these was described ; some appear to be altered basalts, others 

 andesites, one is a felsite, another a diorite. A group of outlying 

 igneous rocks in the vicinity of Narborough was described. Of 

 these, one is a quartz felsite with some hornblende ; another varies 

 between this and a quartziferous syenite ; the rest are syenites, and 

 one contains so much plagioclase as to be almost a diorite. One of 

 the above, near En derby, is seen to be distinctly intrusive in an 

 altered slaty rock, which the authors have no doubt belongs to the 

 Forest series. This discovery proves the igneous character of these 

 rocks also, and extends the area of the slaty series five miles further 

 south than was previously known. A section was devoted to the 

 faults of the Forest region. Here the principal fault runs along the 

 anticlinal axis, with a downthrow on its eastern side which di- 

 minishes from 2500 feet at the north end to 500 feet at the south 

 end. East of this the beds seem undisturbed, but on the west they 

 are shattered by many faults, whose course cannot be traced. These 

 are most numerous near Whitwick. The anticlinal fault is Precar- 

 boniferous. 



In conclusion, the age of the clastic and of the igneous rocks was 

 discussed. The authors inclined to the opinion that the former are 

 of the same age as the Borrowdale series of the Lake-district 

 (Lower Silurian), but admitted that the recent discovery of agglo- 

 merates in the Precambriam rocks of Wales, and in the probably 

 Precambrian ridges of the Wrekin district, weakens the arguments 

 for this correlation. They do not think that there is any reason for 

 supposing them Cambrian. If the Charnwood series is Lower 

 Silurian, they think it most probable that the syenites and tlie 

 Quornden granite were intruded in some part of the Old Red Sand- 

 stone period, and that the later dykes were very probably Postcar- 

 boniferous but Pretriassic. 



II.— January 23, 1878.— Prof. P. Martin Duncan, M.B., F.R.S., 

 President, in the Chair. — The following communication was read : — 



" On the Secondary Rocks of Scotland. Part III. The Strata of 

 the Western Coast and Islands." By John W. Judd, Esq., F.R.S., 

 F.G.S., Professor of Geology in the Royal School of Mines. 



