58 A DESCRIPTION OF THE [Ch. V. 



CHAPTER V. 



DESCRIPTION OF THE SCHISTOSE ROCKS ASSOCIATED WITH 

 GRANITE IN VARIOUS COUNTRIES. 



Mica-slate and clay-slate of the eastern part of Ireland. Their alternations 

 with quartz-rock and hornblende-rock, their associations with granite. 

 The composition of this granite, and its modes of arrangement. The gneiss 



> formation of the Western Isles of Scotland. Its beds of mica-slate, green- 

 stone, compact felspar, clay-slate, talc-schist, serpentine, limestone, and quartz- 

 rock. The nature of their connection with each other and with the gneiss. 

 Abounds in bunches and veins of granite. Description of the primary 

 schistose rocks of Norway, gneiss, mica-slate, clay-slate, with their sub- 

 ordinate beds. They contain immense beds of granite, and are inter- 

 stratified with smaller ones. The primary schistose group of Saxony, 

 gneiss, mica-slate, clay-slate, and shorl-schist. The talcose formations. Of 

 the Alps, including talcose granite or protogine, talc-schist, serpentine, and 

 other magnesian rocks. Of the island of Corsica, composed of granite, 

 eurite, protogine, hornblende-rock, euphotide, talc-schist, serpentine, and 

 analogous rocks. 



IN attempting to show that the primary or crystalline schists 

 of different countries are the equivalents of those of Cornwall, 

 it is not intended to assert that they are all of the same nature, 

 and referrible to precisely the same geological epoch : on the 

 contrary, it is wished, for the present, to avoid all conjectures 

 concerning the nature of their origin, and only to express that 

 these slates do, as in Cornwall, bear a certain relation to the 

 granite with which they are associated; and consequently 

 all slates, both foreign and Cornish, which have the same 

 relative connection and position with the granite, may be 

 regarded as parallel or equivalent rocks. 



These equivalent schists are commonly of a very different 

 nature, which might have been expected a priori ; for even in 

 Cornwall the suites of slates vary when connected with different 

 masses of granite ; still, however, although their composition 

 is not identical, they undergo analogous mutations, resulting 

 from the proportions of the constituent parts, and the manner 



