characters, they are strikingly analogous in almost every essential general circumstance, and that the former may, in a certain sense, be considered as a recent granite; as the granite of the newer strata. ... Thus it is proved that granite, or at least a rock originating in the same causes, may possess the characters of some of the most common varieties of the most recent traps. It remains to reverse the proposition, and to adduce instances of the granitic character among the recent unstratified rocks.

"In the meantime I am unable to perceive that anything is wanting to prove the identity of origin in trap and granite. It is little likely, at least, that geology will often furnish us with evidence of a more decided nature. Nor is it an indispensable requisite to this argument, to produce numerous examples; since there are innumerable cases in science, among which this seems one, where one or two facts are as decisive as a hundred."*

At another place he says—

"Hence it also is, that rocks preserve the same characters wherever they occur, a circumstance otherwise calculated to excite our surprise. In every other department of nature, her productions vary according to the climate and situation, but granite is the same in Egypt and in Greenland."

And again, still further on, he adds

"In examining the revolution of the earth, I have rendered it probable, that there has been granite, or an analogous substance, prior to all strata, and the original source of the whole."†

Professor Playfair states

"Granite, the fossil now defined, exists, like whinstone and porphyry, both in masses and in veins, though most frequently in the former. It is, like them, unstratified in its texture, and is regarded here, as being also unstratified in its outward structure.

66

'Granite, it has been just said, exists most commonly in masses; and these masses are rarely, if ever, incumbent on any other rock:

Geology, by Dr. M'Culloch, vol. i. pp. 145-160. It is recommended that the reader should refer to the work itself, and peruse the whole chapter, which could not be given any fuller here, although replete with interest.

+ Geology, by Dr. M'Culloch, vol. ii. p 196.

Ibid, pp. 87, 88.

they are the bases on which others rest, and seem, for the most part, to rise up from under the ancient or primary strata. The granite, therefore, wherever it is found, is inferior to every other rock, and as it also composes many of the greatest mountains, it has the peculiarity of being elevated the highest into the atmosphere, and sunk the deepest under the surface, of all the mineral substances with which we are acquainted."

With these copious extracts we shall conclude the evidence, in favour of the acknowledged existence of an amorphous mass of mineral matter beneath all those formations which retain their stratified texture; and, likewise, in testimony of the diversified effects-shown by phenomena appreciable by the senses which resulted from the general convulsion that took place amongst those parts of the earth's crust, when it was caused to revolve around its axis, by the formation of the light and its division from the darkness, on the first day of the Mosaic week. This act of protorotation, as we have so repeatedly inculcated, having, by its centrifugal impetus, produced the universal movement above alluded to, which, in turn, caused the friction and consequent fierce heat which fused the mineral substances; and fitted them, in this condition, for irresistible protrusion into the rents, fissures, and centres of mountains and mountain chains, arising from the extension and breaking up of the earth's surface, to complete its static form of revolution; while the same centrifugal impetus, and the heat thus engendered, co-operated to impel these melted streams into those diversified apertures of enlargement, by which alone they could find vent, and where alone they were required! Thus exhibiting another fine example of a complete chain of cause and effect, which links the external form, peculiar position, and internal structure of these rocks of igneous origin, to the creation of the light and its division from the darkness.

Thus far the Dynamical Theory leads us successfully in our endeavours to account for the earth's formation; but when we attempt to apply it, to ascertain the probable condition of these mineral ingredients, before they were made to issue forth,

* Playfair's Works, vol. i. pp. 95-97.

in universal streams, from almost every point of the globe, to insinuate and wedge themselves into the openings prepared for them, when it pleased the Creator so to arrange it; when we make this application of our theory, we are reminded, that it has more to do with what is, than with what was; and that it can assist us only to infer the original condition of these hidden masses-hidden far beneath the accumulated deposits of the non-rotatory period-by the transformation which the dynamical forces have effected in them.

Perhaps, indeed, the greatest benefit which can be derived from our present labours, in relation to this particular subject, will be to direct us to seek, in the movement, friction, heat, and centrifugal impetus-the inseparable concomitants of the Dynamic Theory-for the true cause of the difference between stratified and unstratified rocks, and every diversified feature of these two great classes.

But even this points onwards, not backwards, and leaves the chief difficulty untouched. We still recognise the necessity of supposing the existence of some universal substratum, on which deposition first began, and which possessed more cohesion than would be produced by mere juxta-position of particles, such as sand, for it had to receive the deposits from the primitive ocean, which now constitute the strata; and to sustain them for countless ages upon its bosom. While, on the other hand, we are forced to confess, that the particles of this substratum must have had sufficient mobility to have admitted of their being put in motion, and of their conducting themselves in all respects as a semi-fluid or ductile mass, even before they had been reduced to that state by the heat resulting from friction; for this could only follow, but could not precede their motion; while, to add to our difficulty, their present crystallized texture forbids the supposition of partial previous fluidity having been produced by water; for if this had been the case, its subsequent evaporation, when driven off in the process of crystallization, would, we are inclined to think, have left these primitive rocks much more porous than they really are.

Indeed, the more we reflect on all the phenomena attending the elevation of continental ridges, and the depression of

oceanic hollows, which seem to reveal to us a state of mysterious elasticity in the internal regions of our globe, and consider at the same time, the scrupulous economy of means to the ends everywhere observable in the works of the Creator, while we are under the conviction, that our planet, like all the other heavenly bodies, is destined to be a pedestal to uphold upon its surface, not a receptacle for containing within. And when we contrast all these motives for a hollow or cavernous structure, with the apparent necessity, according to the observations of some astronomers, of internal density, we are at a greater loss than ever to come to a determination, which might either satisfy ourselves, or be offered for the satisfaction of others; an uncertainty which is by no means lessened, although certainly left open to discussion, when we observe such different opinions upon this very subject, as those we are about to subjoin.

The accomplished author of the Connexion of the Sciences, say's

"But a density so extreme, is not borne out by astronomical observation. It might seem to follow, therefore, that our planet must have a widely cavernous structure, and that we tread on a crust or shell whose thickness bears a very small proportion to the diameter of the sphere. Possibly, too, this great condensation at the central regions may be counterbalanced by the increased elasticity due to a very elevated temperature."*

"It has sometimes," says Professor Whewell, "been maintained by fanciful theorists, that the earth is merely a shell, and that the central parts are hollow. All the reasons we can collect appear to be in favour of its being a solid mass, considerably denser than any solid rock."+

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'Taking water at a temperature of 60° as the unit of comparison," says Professor Phillips, "we find the specific gravity of the superficial parts of the globe, as judged of by weighing the most

Connexion of the Sciences, p. 90.

+ Bridgewater Treatise, p. 50. The remaining part is recommended to the perusal of our readers.

prevalent rocks, to be 2.5. By direct experiment, and comparison of the local attraction of mountains and insulated masses of matter with the general attraction of the globe, the mean density of our planet has been inferred to be about five times that of water. This result is found sufficiently in accordance with astronomical considerations, to allow us to adopt it for geological reasoning.

"The interior parts of the globe must therefore be denser than the exterior rocks.

"From the influence of the earth on the moon's motions, it is inferred, that the internal mass of our planet augments in density towards the centre; the surfaces of equal density being symmetrical with the external spheroidal surface. The materials of the earth have therefore collected round the centre in obedience to the laws of gravitation and rotatory movement, and the internal substances, as having fallen to the lower place when freedom of motion was allowed, would probably be heavier under the same circumstances than the superficial substances, and so forth. . . Now though we

cannot presume that the laws of compression would hold in these bodies to such an extent, enough is known to justify a confident belief, that the mean density of our planet would be very much greater than it is, were not the tendency to enormous condensation in the central masses, counteracted by some powerful agent of expansion, such as heat, or neutralized by some peculiar or unknown constitution of the substances themselves."*

Dr. M'Culloch, when treating incidentally on this, says

"Notwithstanding its inferiority in position, we must not grant, as asserted, that granite constitutes the mass of the globe, or is the lowest rock in existence. Of the interior of the globe we know nothing; but its weight is sufficient to prove, that it is not formed of granite. . . . Some unstratified matter, solid or fluid, does doubtless lie beneath the stratified surface of the earth; but while conjectures are fruitless, it might, if solid, be basalt as well as granite."+

We find others expressing bolder and more startling views of this perplexing subject, derived, no doubt, from the gradual

* Treatise on Geology, pp. 9-11.

+ Vol. ii. p. 87.