372 
PASSAGE OF GNEISS INTO GRANITE. [Ch. XXVI. 
crystalline, but the granite, on the contrary, softer and less 
perfectly crystallized near the junction *. 
It will appear from sections described by M. Hugi, that 
some of the secondary beds of limestone and slate, which are 
in a similar manner overlaid by granite, have been altered 
into gneiss and mica-schist f. Some of these altered sedimen- 
tary formations are supposed, by M. Elie de Beaumont, to 
be of the age of the lias of England, and others to be even as 
modern as the jurassic or oolite formations. 
We can scarcely doubt, in these cases, that the heat com- 
municated by the granitic mass reduced the contiguous strata 
to semi-fusion, and that on cooling slowly the rock assumed 
a crystalline texture. The experiments of Gregory Watt 
prove, distinctly, that a rock need not be perfectly melted in 
order that a re-arrangement of its component particles shoul 
take place, and that a more crystalline texture should ensue. 
We may easily suppose, therefore, that all traces of shells an 
other organic remains may be destroyed, and that new chemica 
combinations may arise, without the mass being so fused as tha 
the lines of stratification should be wholly obliterated. 
In allusion to the passage from granite to gneiss before 
described, Dr. Macculloch remarks, that 'in numerous parts of 
Scotland, where the leading masses of gneiss are schistose, 
evenly stratified, and scarcely ever traversed by granite veins, 
they become contorted and irregular as they approach the 
granite ; assuming also the granitic character, and becoming 
intersected by veins, numerous in proportion to the vicinity of 
the mass. The conclusion,' he adds, 'is obvious; the fluid 
granite has invaded the aqueous stratum as far as its influence 
could reach, and thus far has filled it with veins, disturbed its 
regularity and generated in it a new mineral character, often 
absolutely confounded with its own. And if the more remote 
beds, and those alternating with other rocks, are not thus 
* Elie de Beaumont, Sur les Montagnes de FOisans, &c, Mem. de la Soc. 
d'Hist. Nat. de Paris, tome v. 
t Natur. Historische Atyenreise, Soleure, 1830. 
