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Show 240 CHALK AND FLINTS. period r1ecessary for that, and also for the deposttatwn in the places wh0re it is found, must have been considerable; and nothing but an action of the s~a could have given the surface the form which it st1ll has, notwithstanding all the action of art and of the weather. But though we could explain by the action of river and estuarial resistance, aided by the winds, all the formation of these alluvial strata, we are not a jot nearer the formation of solid rocks than ever, Nay, when, as we must, we have recourse to the action of the sea, even though that sea had constantly outraged the angry monsoon at the Cape, or out-eddied the Bay of Biscay, the whole process would be change rather than formation-the destruction and breaking down of rocks, and not the consolidation. Even if the chalk is sea-shells, and the flints are sponges, a goodly pressure must have been required to bring them into their present state; and therefore to seek for their origin, we must examine downwards into the deep. What the condition of the sea was, when it covered all the land,-for, whether all at the same time or not, the sea must have covered all the land, and covered it to a great depth at some time or other,we cannot say. The mountain limestones would lead us to suppose that it contained shelled animals of some kind or other, long before one foot of the dry land appeared above it.s surface; and the oolites, · and many other formations, leave not the least doubt that they were under the waters, inasmuch as they contain shells, and skeletons, and entire fishes, which are adapted for the deep water. The mean level of the sea may be taken as the line of greatest fertility both in the water and on land, and both in the animal and the vegetable kingdoms, because it is the line of the greatest action of hoth the sun and the air. It is probable that tho ca sinks down as much below that line in propor .. FERTILITY OF THE SEA. 241. tion to. the e~t~nt of its surface, as the land rises above.tt ;. e1:nd 1t ts also probable. that the fertility of the sea dtmuushes as ~he. depth mcreases, just as that of the land do~s :With ln?rease of height. But it is probable, nar, l.t ~s certam, that the fertility of the sea cannot d1m1msh so rapidly as that of the land. becaus.e, as w~ descend there are pressure and con2 densatwn, whtch are sources of sensible heat while as :we ascend, there are elasticity and exp'ansion: whiC~ are sources of sensible cold. Thus it is neither 1mprob~ble n~:>r unphilosophical to suppose, that · though t~e mhabttants of the sea vary at different det>ths, JUSt as those of the land do at different h~1g~ts, yet t~at the sea may be well replenished wtt~ 1ts pecuhar plants and animals at depths measurmg more th~n the height of the highest mountain. Conseq~ently, tf we carry our imagination backward to the hm.e when the uniform solid spheroid was co~e.red wtth the two miles of water, we are upon legitimate ~round when we say that the surface of that sphermd unde: the water may have been abundantly. stocked wtth plants and animals, and the ~ater Itself as abundantly as any part of the ocean 1s at present. V·i e cannot know what was the condition of the water at .that early stage of our globe's historywhether 1t was fresh, or impregnated with saline substances as 3:t the pr~sent day. Many of the hlants, the remams of whtch are found in the strata,. ave more the character of fresh-water aquatics than of plants now found in the salt sea. The fishes also have, many of them, the characters of freshwater fishes; ~nd as for many of the shells thouo-h we know but little of their inhabitants, perh~ps th~y are as mnch adapted for fresh water as for salt Wh~n we take all those circumstances into consid: eratwn, we. maJ: perhaps be warranted in saying that the sea whtch, m those primal days rolled over the whole globe, was water in a mu~h more simple X . |