ROCK. 
it, as well as in the other floetz formations, are 
green-stone, amygdaloid, pitch-stone, obsi- 
dian, pumice, compact felspar, clay-stone ; 
gravel, sand, and clay; sand-stone, clay 
iron-stone, lime-stone, iron-clay, and coal. 
The form, and other visible characters, of 
many of the mountain rocks are frequently 
sufficient to point out their nature to the 
attentive observer. Granite is characterised 
by its very high and precipitous cliffs and 
peaks; gneiss is less lofty, and its sum- 
mits are less steep and abrupt; and the 
mountains of mica slate are still less lofty, 
and bear more of a rounded form. Clay- 
slate mountains are generally less lofty than 
those already noticed, and their cliffs are 
still less steep • and rough. Primitive lime- 
stone sometimes presents lofty peaks, like 
those of granite ; but the mountains con- 
taining it in general assume the characters 
«f gneiss, mica-slate, or clay-slate, with 
which it is in general found. Rocks of pri- 
mitive trap are generally lofty, steep, and 
conical. “No rock,” Mr. Jameson ob- 
serves, “ presents a greater variety of ex- 
ternal appearance than the sand-stone. Its 
vallies are deep, rocky, and romantic ; its 
hills are conical, steep, and cliffy ; and it often 
presents grand colossal pillars,'which, from 
their number, and variety of their shape, 
form most striking rocky scenes.” Floetz 
lime-stone assumes very different forms from 
those already particularised, being extended 
in large, flat hills, intersected by steep val- 
lies. Chalk in some situations forms hills of 
Considerable height, which are generally 
rounded, with an extensive base. 
The position, extent, and direction of the 
several strata of different formations, either 
taken with or without reference to the fun- 
damental rock, yield very convincing testi- 
mony in favour of the opinions delivered by 
the celebrated Werner respecting the for- 
mation of the earth. (See Geology.) 
Previously to viewing the illustration of his 
theory in the formation of a suite of rocks, 
it may be necessary to particularise some 
of the peculiarities in the formation of dif- 
ferent rocks, and to show the different terms 
by which they are expressed. The forma- 
tions themselves are distinguished as uni- 
versal or partial, and as unbroken or broken. 
The strata are considered as conformable 
or unconformable, with the direction of the 
fundamental rock ; and overlying, when 
lying over the ends of the strata of the fun- 
damental rock. They are said to be straight, 
when disposed in one direction on the fun- 
damental rock : when they turn round it, 
He^iving the top uncovered, mantle-fprmed ; 
and when they also cover its extremities, 
saddle-formed. When concave, they are 
termed basin-shaped ; and if the concavity 
is long, trough-shaped. Their upper ex- 
tremities, appearing at the surface of the 
earth, are termed the outgoings of the stra- 
ta : the outermost of the circles formed by 
these is the oldest in the concave (the basin 
and trough-shaped), and newest in the. con- 
vex (the mantle and saddle-shaped). When 
detached portions occur on the summits of 
hills, tliey are called caps ; when filling up 
hollow spaces, up-fillings ; and when only 
on one side of a mountain, shield-formed. 
It has been here said, according to the 
theoiy of Werner, that one class of mountains 
was deposited, by chemical formation from 
an aqueous solution, previous to the crea- 
tion of vegetables and animals : that to these 
succeeded another class, in which materials 
mechanically separated were discoverable 
formed during the passage of this globe into 
a habitable state ; and that during the exist- 
ence of animals and vegetables in consider- 
able number, another (the latest) class was 
produced, in which mechanical deposits 
and remains of organized bodies exist in 
considerable quantity. Of tliese different 
classes of rocks, it may be expected, that the 
rocks of the earliest period would be found 
invested in various modes by those of later 
formation, and disposed in the order of 
their separation from the waters from which 
they derived their origin. 
The rocks which exist in the Hartz ap- 
pear to be beautifully illustrative of this 
successive deposition. In the centre a vast 
mass of granite rises through the other stra- 
ta, and round this clay-slate is disposed in 
mantle-shaped strata. Gneiss and mica- 
slate not existing in this country, transition 
limestone succeeds to the clay-slate, and 
then grey wack6 and grey wack6 slate : the 
whole being wrapped round the granite in 
mantle-shaped strata, and invariably with 
lower and lower outgoings, corresponding to 
the newer and newer strata. To these the 
floetz rocks succeed, the oldest of the floetz 
resting on the newest of the transition ; and 
the different floetz rocks resting on each 
other according to their relative age. Last 
of all, the alluvial rocks ,are found in the 
lowest situations. We have thus, as Mr. 
Jameson observes, all the series of rocks, 
from the granite to the alluvial, marked 
with a diminishing level, in proportion to 
the newness of the strata. 
The system of Werner, formed upon a 
most comprehensive view of the several 
phenomena obseryable in tlie formation 
