290 ANNUAL HECORD OF SCIENCE AND INDUSTRY. 



ceeding Pebidian with the Huronian. These Huronian rocks 



are well displayed in Anglesea,both near the Menai Bridge and 



at Holyhead ; while between these, near Ty Croes, the ancient 



gneissic series and the Arvonian orthofelsites may be studied 



to advantage. 



SCOTLAND. 



Hunt has also pointed out the existence of Huronian rocks 

 near Lough Foyle, in the north of Ireland ; and in Scotland 

 in various parts of Argyleshire and Perthshire, as along the 

 Crinan canal and in the vicinity of Loch Etive and Loch 

 Awe. They are, moreover, met with, together with the Lau- 

 rentian gneisses, in the island of Islay. 



The crystalline schists of the Scottish Highlands, like the 

 similar ones in the Atlantic belt of North America, had been 

 described as altered Paleozoic rocks, a view maintained by 

 most British geologists, though opposed by Nicol. Hicks 

 has lately examined a section near Loch Maree, in Iloss- 

 shire, where gneisses were said to overlie, to the eastward, 

 the fossiliferous Cambrian strata. He has found that these 

 supposed gneisses are uncrystalline sediments, very distinct 

 from the truly crystalline gneisses and schists which appear 

 farther to the eastward, in the section. The various sedi- 

 mentary strata, including the fossiliferous Cambrian lime- 

 stones of the region, here occupy a trough in the pre-Cam- 

 brian rocks. The massive basal Cambrian conglomerates 

 along the western border of the trough rest upon the funda- 

 mental Lewisian (Laurentian) gneiss, the ruins of which pre- 

 dominate in the conglomerate, accompanied, however, by 

 fragments of Pebidian (Huronian) rocks. 



IRELAND. 



Hunt has examined the granitic and rnica- schist series 

 which forms the Dublin and Wicklow, or southeastern, 

 mountain- belt of Ireland. These rocks, which include in 

 the mica-schists alike indigenous granitoid gneisses, erupt- 

 ed granites, and endogenous granitoid veins, have been de- 

 scribed, like the crystalline schists of Wales and Scotland, as 

 altered Lower Silurian (Cambrian, Sedgw.), but apparently 

 with no better reason. The adjacent Lower Cambrian sand- 

 stones and shales of Bray and Ilowth are wholly uncrystal- 

 line, and the mica-schist series is by Hunt regarded as pre- 



