160 R O 
have been produced in the same manner as the seams of dis¬ 
tinct concretions, or the surfaces of crystals. These strata, 
collected in groups, give rise to formations, such as gneiss 
or mica-slate and in those cases where the rock is not dis¬ 
tinctly stratified, it exhibits such characters as point it out in 
an unity or formation in the grand series, of which the crust 
of the earth is composed. The rock formations in primi¬ 
tive countries, although well marked and distinguished by 
their general and particular characters, are not in any case 
isolated or unrelated to each other; on the contrary, we find, 
as they approach and join each other, gradual transitions of 
the one into the other, or intermixtures and interlacings at 
their great lines of junction. No true primitive rock appears 
foreign to the others, or exhibiting such characters as inti¬ 
mate a different mode of formation. Thus granite, which 
some consider a kind of lava, and therefore formed in differ¬ 
ent manner from gneiss or mica-slate, passes into and is in¬ 
termixed with the surrounding rocks, and therefore has been 
formed in the same manner. 
Primitive rocks are distinguished from those of the suc¬ 
ceeding classes, by the absence of all fossil organic remains. 
This important fact allows us to infer, that organic beings 
had not been called into existence during the formation of 
primitive rocks, so that there was a time, in the history of 
the formation of our planet, when plants and animals did 
not exist. Although no traces of organic life occur in pri¬ 
mitive rocks, yet they afford beds of a kind of coal (glance 
coal), almost entirely composed of carbon, a substance 
which many consider as peculiar to the organic kingdom, 
and which, they maintain, when found in the mineral king¬ 
dom, is to be traced to previously existing organic beings. 
This opinion is disproved, not only by the facts already 
mentioned, but also by the occurrence of carbon in horn¬ 
blende, slate, and other minerals of the primitive class. 
Here, then, we have the formation of carbon, independent 
of the agency of animals and vegetables. 
Limestone has been by many considered as entirely the 
result of animal action, and the various formations of that 
rock, whether in primitive or secondary mountains, are 
viewed as accumulations of altered shells or corals. But 
neither shells nor corals occur in primitive mountains, al¬ 
though they often contain extensive beds of limestone; and 
further, lime enters as a constituent part into most of the 
simple minerals of which primitive rocks are composed, 
facts which show that lime, like carbon, is an original sub¬ 
stance in primitive mountains, and therefore has been formed 
at times independent of animals. 
The two most abundant alkalies, viz. natron and potash, 
occur in primitive mountains, but of these, the potash is by 
far the most frequent and abundant. Before the discovery of 
potash in lepidolite, a primitive mineral, by Klaproth, this 
alkali was considered as entirely a production of the veget¬ 
able kingdom; but no vegetable remains occur in primitive 
rocks; and, therefore, in this case, the potash has been 
formed by some other agency than that of vegetation. 
Phosphat of lime, which forms so important a constituent 
part of the higher animals, was long maintained to be exclu¬ 
sively a production of the animal kingdom ; its after dis¬ 
covery in some vegetables, demonstrated that it also was 
occasionally produced in some tribes of plants; but still it 
was believed to be, in every case, either of animal or veget¬ 
able origin. But geologists, by the discovery of apatite, or 
phosphat of lime, in primitive mountains, have proved its 
existence in nature, independent of the agency of the organic 
kingdom. 
Primitive rocks abound very much in metalliferous mine¬ 
rals, and hitherto no metal has been met with which does 
not occur exclusively, or occasionally, in this class of rocks. 
Tin, wolfram, and molybdena, occur more frequently in 
these rocks than in other situations. Gold, silver, lead, 
copper, iron, cobalt, zinc, manganese, arsenic, and mercury, 
occur either disseminated, in beds, veins, or imbedded, in 
various rocks of this class, and many primitive districts are 
particularly characterized by the metalliferous repositories 
C K. 
they contain; thus, the primitive district of strontian is 
characterized by its particular venigenous formation of 
galena, or lead-glance; the primitive country of Konigs- 
berg, in Norway, by its group of veins of silver-ore; and 
the primitive gneiss rocks of Arendal and Lapland, by their 
beds of magnetic iron-ore. 
Many of the richest and most important mines in the 
world are situated in primitive rocks; statuary marble, and 
the various granites, porphyries, and serpentines, so much 
valued in the arts; and the gems, so distinguished by their 
beauty of lustre, colour, and great hardness, are principally ■ 
contained in formations of the primitive series. The dia¬ 
mond only is wanting. 
The different species of primitive rocks are very simple in 
their nature, being generally composed of not more than five 
minerals, viz. quartz, felspar, mica, hornblende, and lime¬ 
stone. Some rocks are composed of but one of these simple 
minerals, as quartz rock ; others of two, such as mica-slate, 
which is a compound of mica and quartz; ahd others, as 
granite, consist of three of them, viz. quartz, felspar, and 
mica. In determining the species of primitive rocks, we 
must have an accurate acquaintance with the five simple mi¬ 
nerals already enumerated, and with the aspects they assume 
when forming these aggregate mountain rocks. This being 
the case, nothing more is necessary than to refer the reader 
to the characters of these simple minerals given in the article 
Mineralogy: and now to give short characters of the 
rocks themselves, 
1. Granite is a granular compound of felspar, quartz, and 
mica; syenite is a variety of granite, containing, besides the 
ingredients already enumerated, also hornblende. 
2. Porphyry is an aggregate rock, having a basis or 
ground containing imbedded grains and crystals of felspar, 
and sometimes of quartz and hornblende. 
3. Trap. —All the rocks of the primitive class in which 
hornblende is the predominating ingredient are named trap. 
On exposure to the air they assume the form of steps of a 
stair, hence the name trap. When the hornblende is asso¬ 
ciated with felspar, it forms greenstone; if unmixed, horn¬ 
blende rock; and if slaty, hornblende slate. 
4. Serpentine is a dark green rock, with a splintery frac¬ 
ture, and glimmering or dull lustre, translucent on the edges, 
and so soft as to yield readily to the knife. It is conjectured 
to be a compound of felspar, and of a mineral of the nature 
of hornblende, named diallage. 
5. Limestone. —This rock has generally a white or grev 
colour, is composed of shining granular concretions, and is 
more or less translucent. It frequently contains scales of 
mica, and grains of quartz. 
6. Gneiss is a granular slaty compound of felspar, quartz, 
and mica. 
7. Mica-slate is a slaty compound of mica and quartz. 
8. Clay-slate is a slaty rock, generally composed of ex¬ 
tremely minute scales of mica. It is the roof*slate so well 
known in the arts, ' 
9. Quartz-rock. —This rock is almost entirely composed 
of quartz, either in granular concretions, or in the compact 
state; and grains of felspar and scales of mica are frequently 
contained in it. 
Transition Rocks, or those of the second class, generally 
occupy a higher level than the secondary, but a lower one 
than the primitive formations. Their mountains, mountain- 
ranges, mountain-groups, and cliffs, are more rugged than 
those of the secondary class, but are less rugged and softer in 
their outlines than the primitive rocks. Their valleys, too, 
are wider, and their sides less fugged and abrupt, than in 
those of primitive mountain-groups. 
Most of the rocks are distinctly stratified, and the strata 
are frequently vertical, and, like those of the primitive class, 
exhibit the same general direction throughout great tracks of 
country. Thus the strata in the great high land which 
ranges from St. Abb’s Head to the Irish Sea, and which is 
almost entirely composed of transition rocks, range every 
where nearly from north-east to south-west. 
Although 
