CHAP. IX.

and, during the ages which have elapsed PART III. since that last revolution, that marine matter might have become moulded in close adhesion to the upper mass, and have become hardened into rock of one or other of those species; presenting the appearance of a bed, on which the granite has more recently been formed. Thus, the superposition of the granite, would turn out to be, the subposition of the secondary rock; and the phænomenon would fail to prove, what the chemical argument would endeavour to prove by it.

Or, 2. if, in the violent circumstances attending, or concluding, the second revolution, any vast dislocations of the "rude frame-work of "the globe took place, as they did in the first revolution; the overthrow and projection of a granite mass or masses on the bed of the sea, abundant in marine matter and organic productions, would produce the same sensible appearance at the present day; and we know, that shell limestone constitutes the soil of parts of the Scandinavian peninsula 1. Thus, then, mechanical causes were capable of producing the sensible effect, which the Neptunian geo

'JAMESON's Mineralogy. Ind. Shell limestone.

PART III. logy determines arbitrarily and precipitately to chemical; and in so far they nullify its induction.

CHAP. IX.

And it is the more surprising, that the possibility of this mechanical cause did not suggest itself to our able mineralogist; because he himself reports, that immense masses or fragments of primitive rock, of double the bulk of the Norwegian granite1, are found in the valleys of the Alps, which have been disunited from the parent mass, and have been "evidently

transported" to a bed of secondary formation. This fact, the Mosaical geology guides us to interpret. The mineral geology is forced to ascribe all such transports to the agency of water; because it can find no other impulsive force of equal power. Now, if in the first Mosaical revolution, by which the primitive sea was formed, the convulsions which caused so general a breach and depression of rocks and soils had shattered and separated some masses of primitive rock, without dislodging them from their base; and if, in the agitations of the ocean in the second revolution, when it was draining from its former bed, its violence at length displaced those separated portions from their base, and

1

Comp. D'AUBUISSON, i. p. 232, and ii. p. 228.

CHAP. IX.

projected them into the sea-bed in which PART III. secondary formations had been in course of production for 1656 years; then, the result must have exhibited the general phænomenon which is to be explained, whether in Norway, or in the Alps; varying only in details, equally open to investigation. It will therefore be wise, to observe the caution which the same geologist prudently suggests upon this subject: "Let us wait until a positive and accu"rate observation has proved, directly or in

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directly, the superposition of a granite forma"tion upon strata containing relics of organic beings; before we displace it from the class, "to which observation has hitherto assigned "it 1."

1

CHAPTER X.

CHAP. X.

PART III. THE forms of valleys exhibit phænomena, which, in the view of the mineral geology, suppose physical operations that cannot be limited to the periods of time and the revolutions represented in the Mosaical geology and chronology. It is especially in the formation of valleys, that this science observes; "Time, which has such "narrow limits for us, has none for Nature; for her, it is as indefinite as space: both surpass

even the conception of our imagination1!" In assigning therefore a cause for those formations, it makes the indefiniteness of time answerable for the soundness of its conclusions. To reduce that indefiniteness of time into finite parts and smaller measures, it has indeed suggested, for our convenience, what it terms ecliptic days, borrowed from the archives of the old Chaldaic philosophy: "If (it says) the dif "ferent epochas or revolutions in which our

planet was reduced from a chaotic state to its present habitable form, be measured by those

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great ecliptic days, (each consisting of above PART III. 20,000 years,) sufficient time will be allowed "for the various changes 1."

This is very

accommodating; but, one material thing is here forgotten, which defeats the whole intent; and that is, to inform us who it is that has authority, either to use that measure, or to make that allowance: for certainly, it is not left ad libitum of the mineral geology.

There is no article in geology, in which the mineral system betrays more manifestly its need of a guide to conduct it, with relation both to fact and time, than in speculating upon the causes which produced valleys. Let us hear it pronounce its own speculations upon this subject. "The disposition, direction, and "structure of valleys, their form, the stratifica"tion of the mountains which border them, are indications of their origin. Every body "has remarked the manner in which rain-water, especially after a violent thunder-shower, "furrows the surface of hillocks, or any ground

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presenting a sloping surface. In the disposi"tion of these minute ravines relatively to the declivity on which they occur, in the "sinuosities and deviations of their directions, "in their ramifications, in the form of the

! BAKEWELL, Elem. of Geol. p. 429.

CHAP. X.