8 GEOLOGICAL MEMOIRS. 
morphic. The inferences to which these observations naturally lead 
are the same as those which Darwm drew from the phznomena he 
observed in the gneiss formation of America above alluded to. The 
gneiss-granite of the Alps and the granulite formation of Saxony may 
also be adduced as very striking instances in support of the view 
that many kinds of gneiss must be considered rather as eruptive than 
as metamorphic formations. 
It is well known that the central cham of the Alps contains very 
massive and widely-extended beds of a peculiar gneiss-granite, ex- 
hibiting in many places not only a very distinctly recognizable parallel 
texture or foliation, but also separating into tabular masses or strata, 
parallel to that foliated texture. Lardy therefore calls this rock in 
this place, as well as where it occurs in St. Gothard, unhesitatingly 
gneiss ; and Studer describes it as a peculiar variety of granitic rocks, 
under the name of Alpine granite*. 
On the road over the Grimsel, from Guttannen to Obergestelen, and 
from Airolo by Hospenthal to Amsteg, I had an opportunity of ex- 
amining this remarkable formation of gneiss-granite. The rock, it is 
true, is very like granite, but it usually shows a tendency to a short 
foliated texture, and is separated into very regular beds, the surfaces 
of which often exhibit an appearance quite like that of gneiss, and 
even occasionally that of mica-slate, and between these there fre- 
quently occur regular beds of true gneiss, and even of mica-slate. In- 
some localities, as for example near Gestinen, the foliated texture and 
stratification disappear, and the rock becomes a perfect granular 
granite, without any trace of bemg separable into beds. 
From Airolo to Hospenthal we pass over, as is well known, a fan- 
shaped or synclinal system of beds, the most northerly wing of which, 
having a dip to the south, may be followed much farther, and the 
gneiss-granite from Guttannen to Obergestelen forms a similar system 
of beds. The axis of each system is marked by vertical beds, from 
which those on both sides have a gradual fall to an angle of 70°. 
The beds thus always exhibit a tendency to assume a vertical position. 
If the rock be more closely examined, we find that where it is foh- 
ated, it shows a more or less distinct strike ; this may be perceived even 
in the granite-like gneiss, but it may be most clearly seen on the long 
foliated surfaces where the rock is split into flags. The direction of 
this stretching coincides everywhere very nearly ‘with the dip, or, what 
is the same thing, with the rise of the beds. The rock exhibits there- 
fore, not only in its general structure but also im its texture and _ 
in all the minute details of its constituent parts, a decided tendency 
to a vertical position. 
Every theory of the formation of this gneiss-granite in the Alps, 
may assuredly be required to explam in some measure a condition 
of texture at once so general and so regular. The doctrme of 
metamorphism may perhaps find a poor support im the stratification 
and foliation of the rock, but certainly is not able to assign any 
sufficient cause for the stretching or tension. This appearance, 
* Lehrbuch der physikalischen Geographie, s. 331. 
