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I have stated that they had, doubtless, an important office to perform iu nature; and can it be unreasonable to believe that the earth itself is the great storehouse where the materials that form its surface were prepared, and from whence they were thrown out upon the surface in an igneous, aqueous, or gaseous state, either as melted lava, or in aqueous solution, or in mechanical admixture with water in the form of mud, or in the comminuted state of powder or sand? Inflammable and more volatile substances may have been emitted in a gaseous state, and become concrete on the surface.

"These primaival eruptions, judging from the size of the ancient fissures and craters, may havebeen sufficient to cover a large portion of the globe. Nor can it be deemed improbable that still larger and more ancient craters have been entirely covered by succeeding eruptions. In proportion as the formation of the surface advanced, these eruptions might decline and be more and more limited in their operation.

"It is not necessary to suppose that these subterranean eruptions consisted only of lava in a state of fusion. The largest active volcanoes at present existing, throw out the different earths intermixed with water in the form of mud. Nor should we limit the eruptions of earthy matter in solution or suspension to volcanic craters ; the vast fissures or rents which intersect the different rocks, may have served for the passage of silicious solutions to the surface. We know of no instance in nature of silicious earth being held in aqueous solution, except in the waters of hot or boiling springs; and hence it seems reasonable to infer that many silicious rocks and veins have been deposited from subterranean craters at a high temperature. Calcareous or cretaceous matter is also ejected during aqueous volcanic eruptions. According to Ferrara, streams of liquid chalk, or chalk in the state of mud, were ejected from the mud volcano of Macaluba, in Sicily, in 17*17, which in a short space formed a bed several feet in thickness. Beds of limestone may have been formed by similar calcareous eruptions, in which the lime might be sometimes in solution, and sometimes mechanically suspended ; and the numerous remains of testaceous animals in limestone appear to indicate that the calcareous solutions were favorable to the growth of animals whose coverings contain so much calcareous matter. Nor is it necessary to suppose that these aqueous eruptions were always sudden, and attended with violent convulsions, for when a passage was once opened they may have risen slowly, and have been diffused in a tranquil state, and by gradual deposition or condensation, may have enveloped the most delicate animals or vegetables without injuring their external form.

"If the geologist can admit such a condition of the ancient world as above described—a condition which on a smaller scale might be proved to have existed since the period of authentic history ; if he will further admit, that before the formation of chalk, a great portion of what is now England and the northern continent of Europe, was covered by a deep ocean, interspersed with islands and surrounded by ancient continents—and this few modern geologists will deny—then if we allow submarine aqueous eruptions of calcareous matter either in solution or mechanical suspension, and eruptions of silicious solutions from thermal waters, to have been poured over the bottom of this deep and ancient ocean, we shall have all the circumstances required to form thick beds of chalk, interspersed with layers and nodules of flint. . . .

"My object in directing the attention of geologists to this subject, is to show that strata may be formed more rapidly than they are generally disposed to believe; and that the feeble operations of natural causes in our own times, however similar in kind, bear no proportion in their intensity to the mighty agents that have formed the ancient crust of the globe."—BakewelVs Geology, pp. 351-355.

A similar suggestion in respect to the origin of limestone was made by Mr. Featherstonhaugh, in his Report in 1835.

"The general deposits of calcareous matter on the globe have been by some persons attributed to the exuviae of animals, without stopping to inquire whence those animals derived the solid parts they have left behind them. As we know not that animals have the power of forming lime from other mineral elements, we are compelled to suppose that the calcareous matter forming their osseous structure, their testaceous and crustaceous coverings, preceded them. In considering the primitive rocks, we have perceived that forces of great power, and unknown in modern times, have been in action in the earlier periods of the planet—forces which even now continue occasionally to act, though feebly and rarely. As to the manner in which the statuary limestones were produced, there is much ambiguity. We know, however, that mineral springs, both thermal and*cold, deposit carbonate of lime in great quantities, as they come in contact with the atmosphere. The prodigious deposits of this character form a cold mineral water in the Sweet Springs valley in Virginia, which presents one of the most rare geological phenomena; the no less interesting travertine deposited by the Hot Springs of the Washita in Arkansas, both of which localities I visited this last year; and similar phenomena in various parts of the world, render it quite possible that some extraneous calcareous deposits, lying amidst the primitive rocks, have come from the central parts of the earth in a state of aqueous solution, and have subsequently received their high crystalline character from being in contact with ignigenous rocks in an incandescent state. With springs of such a character in action, the animals of those times could be at no loss for calcareous matter in favored localities.

"In the grauwacke we have beds of limestone, derived, for aught we know to the contrary, like the statuary limestone in the primitive series, from solutions ejected from below, alternating with schistose and sandy beds of probable mechanical origin."—FcalherstonhavgKs Report, 1835, on the country between the Missouri and Red Rivers, pp. 20-25.

Such as we have already shown, is the theory in respect to the origin of limestone advanced by Dr. Emmons. We cite from him another passage.

"The opinions of geologists in relation to the origin of limestone have been hitherto unsettled. From the great amount of limestone in the strata which may be inspected, it has been supposed that animals possessed the power of forming it, or of combining its elements. This view or theory seems to be wholly unnecessary; for what reason have we to infer that it is a material less common in the interior of the earth than silex or alumine? And if it is common, it may find its way to the surface by the same means as the materials composing other rocks.

"Leaving here the opinions of other geologists, I will state that there are two points which it will be my object to establish: 1st, That it is a rock of igneous origin; and 2d, That it is unstratified, which follows from the establishment of the first point: or, if the last proposition is placed first—viz. that the rock is unstratified, its igneous origin seems to follow with equal certainty; so that the points to be proved are really reduced to one."—Emmons's Geology of the Second District of New York, p. 38.

He proceeds, accordingly, to establish these points by proofs drawn from the rock in a great number of localities.

Mr. Hall adopts the same theory to account for the formation of some of the sandstones of the western district of this State.

"If we might be permitted to hazard a conjecture as to the changes and their causes going on at the time of the deposition of these different divisions of the Medina sand

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