OCR Text |
Show l90 VEGETATION NO COUNTERPOISE [Ch. XII. If we suppose that the copious discharge fro~ the.nether regions, by springs and volcanic vents, ~: carbomc aCid and other gases, together with the decompos1t10n of rocks, may be just sufficient to counterbalance that loss of matter which, having already served for the nourishment of animals and plants, is annually carried down in organized forms, and buried in subaqueous strata, we beHeve that we concede the utmost that is consistent with probability. When more is . required by a theorist-when we are to1d that a counterpoise is derived from the same source to that enormous disintegration of solid rock and its transportation to lower levels, which is the annual result of the action of rivers and marine currents, we must entirely withhold our assent. Such an opinion has been recently advanced by an eminent geologist, or we should have deemed it unnecessary to dwell on propositions which appear to us so clear and obvious. The descriptions which we gave of the degradation yearly going on through the eastern shores of England, and of the enormous weight of solid matter houri y rolled down by the Ganges or the Mississippi, have been represented as extreme cases, calculated to give a partial view of the changes now in progress, especially as we omitted, it is said, to point out the silent but universal action of a great antagonist power, whereby the destructive operations before alluded to are neutralized, and even, in a great degree, counterbalanced. "Are there," says Professor Sedgwick, ''no antagonist powers in nature to oppose these mighty ravages-no conservative principle to meet this vast destructive agency? Tl~e forces of degradation very often of themselves produce the.lr own limitation. The mountain-torrent may tear up the sohd rock and bear its fragments to the plain below; but there its power is at an end, and the rolled fragments are left behind to a new action of material elements. And what is true of a single rock, is true of a mountain-chain ; and vast regio.ns.on the surface of the earth, now only the monuments of spohatwn and waste, may hereafter rest secure under the defence of a Ch. XII.] TO THE LEVELLING POWER OF WATER, 191 thick vegetable covering, and become a new scene of life and animation. " It well deserves remark that the destructive powers of nature act on. ly upon lin es, wh 1'l e some of t h e grand prm. C.i ples of conservatwn act upon the whole surface of the land. By the pr~cesses of vegetable life an incalculable mass of solid matt.e r Is absorbed, year after year, ft·om th e e1 a s tI' c an d non-elastic fluids circulating round the earth, and is then thrown down upon its surface. In this single operation there is a vast counterpoise to all the agents of destruction. And the deltas of the Ganges and the Mississippi are not solely formed at the ex~ense of the solid materials of our globe, but in part, and I bel.Ieve also in a considerable part, by one of the great conservative operations by which the elements are made to return into themselves*." This is splendid eloquence, full of the enerO'y and spirit that breathes through the whole address :- 0 Monte decurrens velut amnis, imbres Quem super notas aluere ripas, Fervet, immensusque ruit- ~ut .we must pause for a moment, lest we be hurried away by Its tide. Let us endeavour calmly to consider whither it would carry us. If by the elements returning into themselves be meant th . return to hi~her levels, it is certainly possible that a fracti:: of the orgamc matter which is intermixed with the mud d s d d . d. an an eposite m alternate strata in the delta of th G rna h b e anges, y ave een derived by the leaves and roots of plants from such aqueous vapour, carbonic acid, and other gases as had ascended into th e atmosp h ere from lower reO'ions an'd which were not tl fi d · 0 . ' lere ore, enved from the waste of rock' s and their o:ganllc contents, or from the putrescence of vegetables pre 'VI Ious y no un.· sh ed f rom these sources. This fraction and this-a one, may then be deducted from the mass of sol{d lnatter annually transported into the Bay of Bengal, and what re- Address to the Ge 1 · 1 s · o Oglca oclety on the Anniversary, Feb, 1831, P• 24. |