NAUMANN ON GNEISS AND GNEISS-GRANITE. a 
granite have very often had one common origin, and are in fact 
twin brothers. 
It has been well remarked by De la Beche, while treating of the 
gneiss-granites, in which the very close affinity between gneiss-like and 
granite-like rocks is manifested by the transitions and alternations of 
beds, that in such cases one common origin must be assigned to both 
extremes—the gneiss and the granite; for to derive them from two 
sources would be in opposition to the phenomena exhibited*. The 
difference between the two rocks is no other than this, that the one has 
a foliated, the other a granular texture, with probably a variable pro- 
portionof mica. Instead however of endeavouring to trace the possible 
causes of this difference of texture, some have been rather disposed to 
maintain that the gneiss-like parts, merely on account of their texture, 
are metamorphic sedimentary deposits, and, to be consistent in their 
hypothesis, even assign the same origin to the associated granite-like 
parts, while they hold that the greater proportion of other granites 
are undoubtedly of plutonic origin. For this metamorphic action, 
the existence of vast internal seas of red-hot molten matter is assumed, 
and penetrations of the heat, impregnations, cementations and other 
processes are called into action, in order to solve in some degree the 
physico-chemical riddle, how a presupposed region of grauwacke 
had been changed into one of granite and gneiss. And all this is 
maintained without consideration either of the magnitude of the scale 
on which these formations occur, or of the entire absence of any 
distinct assignable cause of the metamorphic action. But if we are 
to suppose plutonic powers and agencies so energetic as to have ela- 
borated the whole rocky pavement of Finmnland or Scandinavia in such 
a manner that the presumed sedimentary beds have been converted 
into the crystalline siliceous rocks that now exist there, we must 
equally suppose that they were exerting the same activity immedi- 
ately under the whole of the sedimentary crust; and their contem- 
poraneous action over so very considerable a space must have been 
attended with the most stupendous effects ; effects of such a nature, 
that it is altogether inconceivable how the different strata should still 
so perfectly retain their several differences, and the individual beds 
their parallelism of structure. 
But there are still several other important circumstances to be 
taken into account. In the first place, there is the highly inclined 
position of the parallel masses or strata in many extensive gneiss 
districts, in which we find them in an almost vertical position, and 
preserving their parallelism throughout so extensive a range of coun- 
try, that a system of such vertical beds, with a united thickness of 
many geographical miles, will stretch to a distance of ten times that 
extent. In the next place, we frequently meet with such beds having 
a fan-shaped arrangement, the central parts being vertical, and the 
exterior parts fallmg towards the centre with a gradually increasing 
slope. Then again we meet with beds of gneiss in some countries 
with wavings and twistiugs so fantastic, that they can only be com- 
* Handbuch der Geognosie, bearbeitet von v. Dechen, p. 548, 
