708 BEPOUT — 1887. 



masses of the kind referred to were deformed after the fashion of the acid lavas 

 descrihed by Serope, then banded and puckered gneissic rocks would necessarily 

 result. He then showed that in the Lizard district the banded rocks of Prof. 

 Bonney's 'granulitic series ' were continuous with masses in which granitic and 

 dioritic rocks could be seen to vein each other in the most intricate manner, and 

 that the constituent bands of the granulitic series were composed of rocks petro- 

 logically identical with those of the igneous comi^lex. He did not mean to imply 

 that the deformation was connected with the intrusion of the plutonic masses. He 

 was rather inclined to regard it as due in the majority of cases to mechanical 

 forces acting posterior to consolidation. The uncertainty which might exist as to 

 the precise conditions under which the deformation was affected did not invalidate 

 the main conclusion, which was that a banded structure in rocks having the com- 

 position of plutonic igneous rocks was no proof that the latter were not of igneous 

 origin. 



9. On the Occurrence of Porphyritic Structure in some EocJcs of the Lizard 

 District. Bij Howard Fox and Alex. Someevail. 



Professor Bonney has described a porphyritic diabase which is seen on the 

 shore at Polpeor, involved in micaceous and hornblendic schists. The authors 

 have traced this rock further, and have recognised a porphjTitic structure in many 

 dykes and intrusions along the coast which cut through the serpentine, and also 

 in the darker bands of Professor Bonney's 'granulitic group and in the actinolitic 

 schists west of Lizard.' 



Descriptions of these various localities were given and illustrative specimens were 

 exhibited. The crystals of felspar are found to be most numerous in those rocks 

 which lie in the closest proximit}' to the gabbros and serpentine. They have their 

 long axes at various angles, and are mostly small except at Parn Voose, Cavouga, 

 and Green Saddle. The felspathic and hornblendic lines often circle round the 

 crystals. 



Without discussing any theory as to the true nature and origin of the whole of 

 the schists, the authors think that the porphyritic structure so prevalent in the 

 dark bands of the ' granulitic group,' in many of the micaceous and other rocks, as 

 also in the later intrusions cutting the serpentine, indicate an igneous origin for 

 many rocks hitherto regarded as schists. 



10. Some prcliminarii Observations on the Geology of Wiclcloiu and Wexford. 

 Bij Professor SoLLAS, LL.D., D.Sc. 



I. Pi-e-Cmnbricm JlocJis. — The existence of these is, as yet, by no means demon- 

 strated : the grey gneisses of the Greenore-point district closely resemble the cor- 

 responding rocks of Anglesey, as Dr. Callaway has pointed out, and are possibly 

 Archfean. The asserted presence of Archrean rocks in the Aughrim section cannot 

 be substantiated. Those regarded as Archaean are crushed igneous rocks, some 

 hornblendic and others felspathic : the latter present themselves as ' augen-schists.' 

 The Howth series is represented in the Carrick district, and in that of Wexford 

 and the Forth Mountains, as well as elsewhere ; it differs from the series exposed 

 in the cliffs of Bray, but is so closely united with the latter that till further evidence 

 is forthcoming the author would regard the two series as forming parts of the same 

 system. 



II. Camhrian Itoclis. — Of late attention has been directed to the Cambrian 

 quartzite, some authors asserting that it has been formed as a deposit from mineral 

 springs, others that it is to be regarded as intrusive in the same sense as an admitted 

 igneous rock. Examination under the microscope demonstrates that in all cases it 

 is merely a somewhat altered grit ; its intrusive appearance may result from its 

 behaviour during the folding of the country : the softer argillaceous rocks may have 

 flowed out in lines at right angles to the direction of pressure, the harder quartzites 

 may have been broken across the line of flow into masses of various dimensions, and 



