THE GEOLOGY OE SWITZERLAND. 2 Q 
matrix, and represent larger crystals or crystalline 
aggregates which have been partially broken down 
and dragged along by shearing movements in the 
rock. 
Granite. 
Granite, like Gneiss, is composed of Quartz, Mica, 
and Felspar, but differs from it in not being foliated. 
Granite is a plutonic rock and may be of any 
age; it often sends veins into the surrounding strata, 
which it then forces out of position, in which case 
they show evidence as they approach it of being 
much altered by heat. It solidified at a considerable 
depth below the surface, and its upper portions pro- 
bably flowed out as lava. It presents much variation: 
if it shows traces of foliation it is known as Gneiss- 
granite. Hornblende-granite contains Hornblende in 
addition to the other elements. Diorite differs in 
containing Plagioclase instead of Orthoclase, and less 
Silica; if the Felspar crystals are large and well de- 
fined, it is known in popular language as Porphyry. 
Syenite consists of Felspar (Orthoclase), Hornblende, 
and a little Quartz. Protogine, so named because 
it was formerly supposed to be the oldest of all 
rocks, is a Granite, containing Sericite instead of, or 
with, ordinary Mica. 
