ON CONGLOMERATED ROCJCS. 



20f 



I» Primitive Conglomerated Rocks. 



The primitive conglomerated rocks occur in 

 beds or Strata of considerable magnitude, in Gneiss^ 

 Mica-Slate, Granite, Porphyry, and Limestone. 



1. Conglomerated Gneiss. 



The gneiss conglomerate, is formed of roundish 

 and angular fragments, or portions of gneiss, horn- 

 blende-rock, felspar, and quartz, connected toge- 

 ther by a ground or basis of gneiss. Sometimes 

 the whole bed has the conglomerated character ; 

 mother instances, only a part of it is in this state ; 

 the other portion, and frequently the largest, be- 

 ingof pure gneiss. This rock occurs near the Castle- 

 town of Braemar in Aberdeenshire, at Valorsine 

 and St Bernard in Switzerland, and also amongst 

 the mountains of Norway, as appears from the 

 following description by Von Buch : The in- 

 terior of the rocks is l^ere not le^s remarkable. 

 At first, the quartz continues from Formo onward. 

 It then frequently resembles porphyry; for there 

 are imbedded in the grey-coloured quartzy basis, 

 dark crystals of quartz, apd the rock is almost 

 every where intersected by drusy fissures. At 

 length, abopt half a German mile from Formo, 

 the gaeiss also makes its appearance in the valleyj, 

 and the quartz rocks disappear. The gneiss rises 

 immediately to a great thickness. The Rosten- 



