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formed by the union of those elements in different proportions. In felspar there are of
Silica, . . . 64-04 Potash, . . . 13-66
Alumina, . . . 18-94 Lime, . . . 0-76
Oxide of iron, . . . 0-74
In hornblende, the proportions are usually
Silica, . . . 45-69 Magnesia, . . 18-79
Alumina, . . . 12-18 Protoxide of iron, . 7-82
Lime, . . . 13-S3 of magnesia, . 0-22
Fluoric acid, ' . . . 1-50*
Several of these elements, however, enter in much larger proportions into the composition of lavas. Thus of the felspathic minerals in volcanic rocks, there are in
Silica. Alumine. Lime. Magnesia. Soda. Iron.
. .... wrt „„ i and a trace of iron, mag
Anorthite, 43-79 85-49 18-93 \ neaia, soda, and potash.
Labradorite, 53-4S 26-46 9-49 1-74 4-10 1-60 and a trace of potash.
Andesin, 59-60 24-23 S-77 1-00 6-53 1-58 1-08 potash.
Alblte, 69-86 19.26 0-46 10-50 0-43"
Orthoclase, 65-72 1857 0 35 1-25 14-02"
Adularia, 65-59 17-97 1-34 1-01 13-99 "t
In the volcanic rocks or lavas themselves these ingredients exist in still different proportions. Thus in trachytes and other volcanic rocks, silica ranges from 49-21 to 73-46; alumina from 12-04 to 20-80; iron
* H. T. De La Beche's Geol. Observer, pp. 34, 35.
t H. T. De La Beche's Geological Observer, p. 352. Daubney's Description of Volcanoes, p. 13.
from 1-49 to 11.84; lime from 0"45 to 8-83; magnesia from 0-39 to 7-96 ; potash from 1-42 to 7-16; and soda from 4-29 to 7-98, with sometimes a trace of manganese.*
In the recent lava of Kilauea, Hawaii, silica ranges from 39-74 to 59-80; protoxide of iron from 16-91 to 33-62; and soda from 4-83 to 21-62.f
In basalt, silica ranges from 44-50 to 59-5; alumina from 11-5 to 17"56: iron from 4-64 to 204
In all these volcanic rocks, which it is universally held are ejected from deep abysses in the earth, all the great elementary substances of which the strata consist are thus conspicuous ingredients. They present the most decisive proofs, therefore, that the various substances that enter into the composition of the strata were placed by the Creator originally in masses in the interior of the earth.
But besides the place which lime holds in these volcanic rocks, it has in some instances been thrown up in masses from the interior of the planet. Thus Mr. Emmons describes many veins, dykes, and larger bodies in the northern section of this State that are undoubtedly of igneous origin.
"The origin of primitive limestone, I apprehend, is precisely the same as that of all the granitic compounds. It is
* De La Beche's Geol. Observer, p. 353.
not as some, perhaps, would be ready to suggest, produced by the overflowing of a molten mass of granite on a sedimentary limestone, thereby decomposing it; and by which portions the most intensely acted on would be raised in a vaporous state, and made to penetrate the mass of cooling granite above. Geologists, in speaking of limestone, seem to be averse to the admission that it may form a portion of the interior of the earth, or even to admit that it may exist there at all; but there seems not a particle of sound reason against the doctrine that it may be as common in the earth as silex, or any of the simple or compound rocks. There is, in fact, more reason to make this inference, for many of the phenomena of nature speak of its being, and proclaim its existence. From what I have seen of it, I am disposed to consider it as one of the igneous products, having its origin in a mode corresponding to all the unstratified rocks, and differing from them merely in the materials of which it is composed."—Emmons's Geology of the 2d District of New York, p. 26.
He accordingly cites a number of localities in which large masses, dykes, and veins of limestone project up from beneath into granite, in such a manner as to render it indisputable that they were forced from below in a state of fusion like the veins and dykes of granite, quartz, trap, and other species that have been driven up from beneath by heat into the primary and secondary formations.
Iron, also, has been ejected from the interior of the earth in masses, as is seen from its existence in rocks that are of igneous origin. Thus of the magnetic oxide Mr. Emmons states:
"Masses of ore appeared to be coeval with the rock which incloses them; or such a view comports best with many facts and phenomena which are brought to light in mining. If this is sustained by future investigations, it will necessarily follow that the original formation must have been influenced by the same agents as those which were concerned in the production or modification of the materials composing the rock. The rock which incloses the ore is clearly unstratified; from which we are also to infer the igneous origin of the inclosed mass of ore. We are clearly driven off from every other mode of formation: the theory of electro-magnetic agency appears out of the question."— Emmons's Geology of the 2d District of New York, p. 90.
Other passages might be quoted from him and others, that present the same fact. We have thus the most indisputable proofs that all the great elements of the strata—silex, alumine, lime, potash, soda, magnesia, and iron—existed originally in the interior of the earth. The materials were lodged there on a vast scale, for the formation by their transferrence to the surface of precisely such composite rocks as those which now constitute the covering of the globe.
Immense masses of these substances that were originally deposited in the depths of the interior, have actually been ejected to the surface, and now form a part of the earth's rocky vesture. Thus all the unstratified rocks—granite, porphyry, greenstone, serpentine, hypersthene, basalt, and all the varieties of trap, as well as the lavas and tuff of modern volcanoes, are universally admitted to be of igneous origin, and to have been elevated from the interior of the earth; and they together constitute a very considerable part of the crust that rises above the level of the sea. The Andes of South America, for example, extending from the Isthmus to Cape Horn, with a breadth of from 30 or 40 to 500 miles, cover, it is supposed, about one sixth of that continent, and rising from three or four thousand to fifteen or eighteen thousand feet, irrespective of the highest peaks, have undoubtedly—with the ranges that lie eastward of them in Venezuela, at the sources of the Oronoco, and in Brazil—several times the bulk of the other parts of the continent that lie above the line of the ocean; and they consist mainly of granite, porphyry, trachyte, andesite, basalt, and other igneous rocks, of which silex, alumine, lime, iron, potash, and soda, are the chief constituents. All these immense masses were thrown up to the surface, it should be considered, subsequently to the deposition of the principal stratified rocks; as is seen from the fact that they bear on their sides and summits vast bodies of the primary,