162 R O 
white sandstone, butnminous shale and slate clay, clay iron¬ 
stone, limestone, and coal. The whole together form a group 
or set of rocks, termed the coal formation. It rests on the 
mountain limestone. 
4. Second Secondary Limestone, or Magnesian Limestone 
of Geologists.—The formation, as it appears in England, is 
generally a granular, sandy, and glimmering limestone, 
which contains a considerable portion of carbonate of mag¬ 
nesia. It occasionally contains gypsum and rock-salt. It 
lies immediately over or above the coal formation. 
4. Second Sandstone, or New Red Sandstone Formations. 
—This sandstone is principally composed of particles of 
quartz, set in a reddish-brown clayey basis or ground. It is 
looser in its nature than the old red sandstone, and its colour 
wants the blueish tint which occurs in the old red sandstone. 
It is sometimes conglomerated, particularly where near the 
magnesian limestone, when it contains fragments of the sub¬ 
jacent strata. It abounds in beds of red and blue marl and 
clay, and in these there are occasionally imbedded masses 
and beds of gypsum, and rock-salt. It is here, and in the 
magnesian limestone formation, that the greatest masses of 
rock-salt are met with, and it is in these formations of the se¬ 
condary series that the principal salt mines are situated. It 
rests immediately on the second secondary or magnesian lime¬ 
stone. 
5. Third Secondary Limestone, or the Oolite or Shell 
Limestone Formation, or Jura Formation.—The lower mem¬ 
bers of this formation are blue, grey, and white slaty lime¬ 
stone, with blue slaty marl, and clay, in which are variously 
shaped masses of chert. These are known under the name 
Lias. Above these, still in this formation, there are 
alternations of beds of oolite limestone, shelly limestone, cal¬ 
careous sandstone, various marls, clays, and fuller’s earth. 
It rests upon the second or new red sandstone. 
6. Third Sandstone Formation, or the Green Sand For¬ 
mation.—This formation extends through a large portion of 
the south-eastern parts of England. Its characteristic mem¬ 
ber is a siliceous sandstone, abounding in grains of a sub¬ 
stance resembling green earth or augite. Besides this sand¬ 
stone, the formation contains beds of a coarse shelly lime¬ 
stone, of various clays, fuller’s earth, and of iron sand, it 
rests upon the third limestone or oolite formation. 
7. Fourth Limestone Formation, or Chalk Formation.— 
The lower part.of this formation is composed of a grey clayey 
chalk, without flints, and of grey coloured clays and marls. 
Immediately above is ahard chalk, with few flints, and above 
is the softer chalk in which flints and organic remains abound. 
8. Brown Coal Formation.—In this formation, which ap¬ 
pears- to rest upon chalk, brown coal occurs in great masses, 
associated with clays and marls, and occasionally with 
glance coal. The English pudding-stone appears to rest 
immediately, either on the brown coal or the chalk formations. 
9. Paris Formation—Under this head we include the 
series of beds of clay, marl, limestone, gypsum, sand, and 
sandstone, that occur in the basin of Paris, and also in that 
of the Isle of Wight and other quarters. They lie above chalk, 
and higher than the brown coal, and are divided into sets; 
two characterized by the presence of fresh water shells, and 
remains of quadrupeds, are named fresh wafer formations; 
and other two, containing principally salt water shells, are 
named marine formations. 
10. Secondary Trap Rocks.—The rocks of this division 
have been described by many geologists as lavas. They 
occur in imbedded masses, beds and veins, in many of the 
formations already described, and hence, in order to prevent 
repetition, we have brought them together under one di¬ 
vision. They are principally composed of augite, with oc¬ 
casional hornblende, and felspar; the augite occurs in all its 
states from the crystalline to the earthy or powdery condi¬ 
tion, and the felspar appears in all the different states from 
clay stone and clay, to the crystalline state. The following 
are the secondary trap rocks: basalt, greenstone, sienite, 
amygdaloid, porphyry, and tuffa. 
Alluvial Rocks.—These are the various clays, loams, marls, 
sands, gravels, rolled masses, &c. which lie over the other more 
C K. 
solid rocks, and which owe theirorigin to the agency of the 
waters of the ocean, of rivers, lakes, and springs. They are di¬ 
vided into those called diluvian, because they seem to have been 
formed at the time of the deluge; such are the clays, sands, 
and loams, containing ther emains of elephants, rhinocerotes, 
&c. and of those loose blocks sometimes 50,000 square feet 
in magnitude, and found at great distances from their native 
places; and into those clays, loams, sands, and gravels, 
which are daily formed on the face of the earth by the 
agency of the waves of the ocean, and the actions of 
rivers, lakes, and springs, and which have been named post¬ 
diluvian. 
Volcanic Rocks.—All those rocks which owe their present 
characters to the action of subterranean heat, or to that ema¬ 
nating from beds of coal, are named volcanic. 
They are divided into pseudo-volcanic, and true volcanic. 
The pseudo-volcanic rocks are clays and iron stones, indu¬ 
rated, and partly melted by the heat from burning beds of 
coal. The true volcanic rocks are those which have flown 
in streams, or have been projected in the form of dust or 
gravel, from the craters of volcanoes. 
For the preceding account, we ha< e been chiefly indebted 
to the works of Dr. Jamieson. We shall now copy from 
Saussure a description of Mont-Blanc, because it affords some 
objections to the theory just laid down, and is also in itself 
highly interesting. 
After having gained the highest point of the mountain, 
the first thing which struck me,” says Saussure, “ in the 
entire view of the high mountainous summits which I had 
under my eyes from the summit of Mont Blanc, (the 
highest of them all,) was the kind of disorder which pre. 
vailed in their disposition. When we contemplate the range, 
of which Mont Blanc forms a part, from less considerable 
elevations, it appears as if these colossal mountains, were situ¬ 
ated in a line, and formed a chain; but this appearance 
vanishes entirely from the bird’s-eye view which is here pre¬ 
sented. The mountains to the north of Mont Blanc, in 
Savoy and Switzerland, are indeed united among themselves, 
so as to form mountain chains, but the primitive mountains 
do not present this appearance. They are distributed in 
great masses, or in groups of various strange forms, detached 
from each other, which appear at least but accidentally 
united, without any regularity. Tlius on the east, the lolty 
peaks called les Aiguilles de Chamouni, the mountains of 
Argentiere, of Courtes, and of Taleul, form one triangular 
group, almost detached from Mont Blanc, and only con¬ 
nected with it at the base by a narrow ridge. 
“ On the south-east likewise, Mount Zuc, I,a Rogue, and 
the other primitive mountains to the north of the summit of 
l’Allee Blanche, form a group nearly triangular, separated 
from Mont Blanc by the valley of the glacier of Miage, 
and which is only connected with Mont Blanc by the base 
of the mountains which close that glacier to the north. 
“■Mont Blanc itself forms a mass almost isolated, the dif¬ 
ferent parts of which are not in the same line, and have no 
relation of fituation with the other groups. 
“ On casting my eyes still further, I confirmed the same 
observation. The primitive mountains of Switzerland and 
Italy, which 1 had sufficiently near to be under my eyes, 
presented only separated masses, or detached groups, with¬ 
out order or regularity. Notwithstanding this irregularity 
in the forms and distributions of the grand masses, J ob¬ 
served certain important resemblances in the structure of 
their parts. All that I distinctly saw, appeared composed 
of plates ( feuiUets ), arranged in the same manner nearly 
from north-east to south-west. I had particular pleasure 
in observing the same structure in the Aiguille du Midi, 
which I had formerly endeavoured but in vain to study, 
being prevented by the inaccessible walls of granite that 
surround the base. I had a view of the Aiguille du Midi 
on the second day of my ascent, and never lost sight of it 
as I proceeded. I assured myself that it is entirely composed 
of magnificent plates of granite, perpendicular to the ho¬ 
rizon, and directed from north-east to south-west. Three 
of these plates, separated from each other, form the summit, 
decreasing 
