R 0 
decreasing gradually in height from the southern race, on 
the side of the Col du Geaun. 
“ When seen from the base, these plates had the appear¬ 
ance of being bent, like the leaves of an artichoke; but this 
must be an optical illusion, for all those which I could now 
see distinctly appeared straight; and if there were any ex¬ 
ceptions, they were only local, and of small extent. 
“ This great phenomenon of the vertical position of the 
plates can only be explained, by admitting- a great over¬ 
turning of the whole mass, which has lifted them from their 
original horizontal position. 
“ Another question, which I wanted anxiously to resolve, 
was also now answered. These great plates of rock pre¬ 
served the same nature and quality at the summit as at the 
base, where I had so frequently examined them. This ob¬ 
servation proves a remarkable property in mountains with 
vertical beds: each bed preserves the same nature from the 
bottom to the top. 
“ From this magnificent observatory I could comprise in 
one view the whole of that great phenomenon—which I had 
before contemplated but in parts—the elevation of the beds 
forming the mountains on the side of Mont Blanc On 
whichever part I turued my eyes, I saw the secondary 
chains of mountains, and even the primitive of the second 
order, raising their beds against Mont Blanc, and the high 
summits in its vicinity. Such were the mountains on the 
north of Repesior, of Passy, of Servoz, and Le Buet; on 
the south, the Col du Ferret, Great St. Bernard, and those 
of the chain of Cremont, more remote,, and beyond the 
mountainous chains, whose escarpments turn to Mont 
Blanc. We saw others, whose escarpments were turned in 
a contrary direction. These appearances are in perfect ac¬ 
cordance with the theory which supposes that the crust of 
the globe has been broken, and the beds of rock raised from 
their horizontal position. It follows from hence, that the 
horizontal distance from the bottom of the valley of Cha- 
mouni (if that were once the ancient surface of the globe) 
should have some correspondence with the height of Mont 
Blanc; and that this distance is nearly the thickness of the 
stony crust, which has been broken and elevated; and that, 
consequently, Mont Blanc, which actually rises about a 
league above the surface, was in its original position buried 
two leagues beneath it.” 
The naked rocks on the summit, which form two kinds 
of arretes or crests of a dark colour, are of granite. The 
felspar in this granite is white, inclining to grey, green, or 
reddish: when exposed to the flame of the blowpipe, it yields 
a colourless transparent glass, but full of bubbles. The 
felspar is sometimes intermixed w'ith a kind of earthy steatite. 
The quartz in this granite is semi-transparent and whitish, 
and appears rather unctuous in the fracture. Very minute 
fragments were rounded by the flame of the blow-pipe: it 
is, therefore, more fusible than rock-crystal. These gra¬ 
nites are also intermixed with green and black hornblende, 
and with chlorite, which seems to supply the place of mica, 
as the latter scarcely appears, and only in minute spangles. 
In some places, these granites graduate into irregularly 
schistose rocks, composed of quartz and felspar, whose 
seams are filled with a brown argillaceous and ferruginous 
earth, that melts into a black glass. The granite on the 
actual summit is composed, like the above, of quartz, fel¬ 
spar, and hornblende or steatite. Felspar constitutes about 
three-fourths of the mass: the hornblende and steatite form 
too small a portion to be estimated, the quartz forming nearly 
the whole of the remaining fourth part. On the northern sum¬ 
mit, besides the above species of granite, he met with a kind 
of trap rock, composed of minute crystals of white felspar 
and hornblende. On the southern summit he also found 
rocks of petrofilex (hornstone), of a pearl-grey colour. It 
is deserving notice, that the definition of these granites, as 
given by Saussure, would, according to the Wernerian 
system, bring them under the denomination of secondary 
granites; though surely, if any granite can properly be 
considered as primary, it is that of Mont Blanc, and the 
mountains in its immediate vicinity. 
C K. 163 
We borrow from Dr. Jamieson’s Geognomy a description of 
two well-known tracks of country, the Hartz, and the Saxon 
Erzgebirge, or metalliferous mountains. 
Of the Hartz.—An immense mass of granite forms the 
centre of this country; it rises through the other strata, and 
is elevated a considerable height above them all, forming the 
famous mountain—the Brocken. Mantle-shaped strata of 
clay-slate are wrapped around this central mass. It is worthy of 
remark, that gneiss and mica-slate, two of the most consider¬ 
able of the older formations, are wanting in this country. To 
the clay-slate succeeds transition limestone, then grey-wacke 
and grey-wacke slate; and the whole of these wrapped 
around the granite in mantle-shaped strata, and invariably 
with lower and lower outgoings, corresponding to the newer 
and newer strata. The flcetz rocks that immediately succeed 
the transition surround them in mantle-shaped strata. Imme¬ 
diately on the newest of the transition rocks rests the oldest 
of the flcetz, the old red sand stone; to this succeeds the 
other floetz formation, in the following order, according to 
their relative age :—first floetz limestone, first flcetz gypsum ; 
second or variegated sandstone, second or newer floetz gyp¬ 
sum, second floetz limestone. These flcetz rocks are the 
links that connect the transition with the alluvial, the next 
class of rocks. These are found in the lowest situations. 
We have thus, from granite to the alluvial formation, all 
the series marked with a diminishing level, in proportion to 
the newness of the strata. 
Of the Saxon Erzgebirge.-—The mine district of the 
Electorate of Saxony has a basis of granite which rises 
through the super-incumbent rocks in the different places at 
Altenberg, Johanngeorgenstadz, and Bobrisch, on the road 
leading from Freyberg to Dresden. The newer formations, 
viz. gneiss, mica-slate, topaz-rock, and clay slate, are 
wrapped around the granite in mantle-shaped strata, and the 
diminishing levels of the outgoings correspond to the newness 
of the formations. Over these we meet with other primitive 
formations that overlie the older formations, and their contin¬ 
uity is partly broken and partly unbroken; here are porphyry, 
sienite, newer granite, quartz, and serpentine. Still lower down 
we meet w'ith transition rocks, of which the limestone appears 
Kalk-grun and Wildenfels ; the amygdaloid at Voghtland ; 
and the grey-wacke and grey-wacke slate near Freyberg. 
Still lower down, and often covering the preceding forma¬ 
tions, we find sandstone and limestone; and in several 
places, as at Hainchen, Pottchappel, near Dresden, and 
Zwickau, there are depositions of the coal formation. Lastly, 
the newest flcetz-trap formation covers all the others in un- 
conformable, overlying, and very broken stratification.” 
Where rocks rise above the surface, and are exposed to the 
action of air and moisture, they are liable to decomposition 
and disintegration. The former consists in the separation of 
the constituent parts; the latter in the separation of the 
integrant parts: the one may be compared to the moulder¬ 
ing of the stones of which a building is constructed; the other 
to the disjointing and dislocation of the stones in a sound 
state, when a building is thrown down. Both these pro¬ 
cesses frequently take place in the same rock. 
The disintegration of rocks is sometimes rapidly effected 
by earthquakes, lightning, and the immediate action of sub¬ 
terranean fires. It is, however, to the more constant opera¬ 
tions of moisture and change of temperature, that the 
destruction of rocks and mountains may be principally attri¬ 
buted ; but no well-authenticated observations have yet been 
made to determine the extent of these effects during a given 
period of time. It has been vaguely stated, that the height 
of the Pyrenees is diminishing about one foot in a century; 
hence it w'as calculated that a milliion years would be 
required to level the rocky boundary which separates France 
and Spain. It is obvious that a lapse of many centuries 
would be required to verify such a conclusion ; and though 
the decomposition and disintegration of rocks are, in many 
situations sufficiently rapid to be observable during the short 
period of a single life, yet, in other situations, rocks present 
the san.e unvarying outline for ages, and preserve their 
angular sharpness, which is natural, or, in some instances, 
the 
