Ch. V.] PRIMARY SCHISTOSE ROCKS. 77 



frequently, until these rocks alternate in equal abundance and 

 extent; but slaty undulating gneiss at last prevails every 

 where." * 



Thus we learn that, in these northern regions, the granite 

 and gneiss are constantly passing into each other ; so that it 

 is often difficult to determine to which of these the rocks are 

 to be referred ; for the slaty structure, which is the grand 

 distinction, is not always to be detected. For example : " The 

 mountain of Luroe is composed of gneiss, and on the whole 

 of the ascent the shining felspar is not concealed between the 

 laminae, as is often the case in these islands. The detached 

 masses would lead one to suppose that the rock of this 

 mountain is granite, but the mixture is too indefinite, and, 

 even in these loose blocks, the slaty structure of the rock is 

 betrayed by the flat position of the scales of mica." t "In 

 the island of Grydoe, the gneiss is distinct and beautiful : the 

 large cubical blocks, at the foot of the cliffs, render it evident 

 that the slaty ingredients have not here their usual ascend- 

 ancy ; the mica is rare, and in small parallel stripes ; the 

 felspar is red and small granular, and the quartz in small 

 quantity and not distinct." :f 



Such are the leading facts concerning the gneiss in the 

 north of Europe. This rock is generally succeeded by mica- 

 slate, with which it alternates, and into which it repeatedly 

 passes, by a gradual change of its mineral characters, just as it 

 does with granite. 



In the rock of the island of Stegen, the felspar is so con- 

 cealed, that traces of it are only here and there visible be- 

 tween the scales of mica; which, however, are not con- 

 tinuous, as is usually the case in the mica-slate, but appear as 

 large scales lying close above one another. It contains gar- 

 nets in great abundance, often as large as hazel nuts ; and 

 beds of granular quartz and hornblende, both with and with- 

 out felspar. This rock constitutes the intermediate link 



* Travels through Norway and Lapland, p. 396. 

 f Idem, p. 149. \ Idem, p. 165. 



