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Show ~40 JMDEDDING OF TERRESTRIAL PI.,ANTS. (Ch. XV. which more seriously impedes the acquisition of just views in the etiology of our science, than an habitual disregard of the important fact, that the reproductive effects of the principal agents of change are confined to another el~ment,-to that larger portion of the habitable globe, from wh1ch, by our very organization, we are almost entirely excluded. Imbedding of Terrestrial Plants. When a tree falls into a river from the undermining of the banks, or from being washed in by a torrent or flood, it floats on the surface, not because the woody portion is specifically lighter than water, but because it is full of pores containing air. When soaked for a considerable time, the water makes its way into these pores, and the wood becomes water-loyged anrl sinks. 'l'he time required for this process varies differently in different woods, but several kinds may be drifted to great distances, sometimes across the ocean, before they Jose their buoyancy. If wood be sunk to vast depths in the sea, it may be impregnated with water suddenly. Captain Scoresby informs us in his Account of the Arctic Regions*, that on one occa-sio'n a whale, on being harpooned, ran out all the lines in the boat, which it then dragged under water, the men having just time to escape to a piece of ice. When the fish returned to the surface '' to blow," it was struck a second time, and soon afterwards killed. The moment it expired it began to sink,an unusual circumstance, which was found to be caused by the wei()'ht of the sunken boat which still remained attached to it. 0 By means of harpoons and ropes the fish was prevented from sinkin(J' until it was released from the weight by connecting a 0 rope to the lines of the attached bo~t, which was no sooner done than the fish rose again to the surface. The sunken boat was then hauled up with great labour, for so heavy was it, that although before the accident it would have been buoyant when full of water, yet it now required a boat at each * Vol. ii. p. 191, Ch. XV.] IMBEDDING OF TERRESTRIAL PLANTS. 241 e:.d to ~eep i.t from sinking. '' When it was hoisted into tile s Ip, t e ~amt came off the wood in large sheets ; and the planks, wluch were of wainscot I . ' were as comp etely soaked in every pore as If they had lain at the bottom of th . the Flood ! A wooden apparatus that . d ehsea sm~e . accompame t e boat m Its. progress through the deep' consistin g c hI' e fl. Y of a p1. ece of tluck deal, about fifteen inches Rquare h d .1! Jl ~ ' appene to 1a over-board, and, though it originally consisted of th 1' ht fi k · 1 e 1g est r, san m t 1e water like a stone · The b oa t was re·n d ere d use-less; even the wood of which it was built b . m d . ' on emg onere to the cook for fuel, was tried and rejected as incombustible* " I Cap&tain Scohresby found that by sinking pieces of fir, ~lm, as 1, c., to t e depth of four thousand and some tI' mes SI·X : thousand feet, they became impregnated wi'tl d 1 sea-water, an when drawn up again, after immersion for a;n hour, would no longer float. The effect of this impregnation was to increase the dim:nsi.ons as well as the specific gravity of the wood, every sohd mch having increased one-twentieth in size and twenty-one twenty-fifths in weight t. When timber is drifted down by a river, it is often arrested by lakes, and becoming water-logged it may sink and be im~ edded in ~acustrine strata, if any be there forming : sometimes a portion floats on till it reaches the sea. In the course of .the Mackenzie River we have an example of vast accumul~ tiOns of vegetable matter now in progress under both these circumstances. In Slave Lake in particular, which vies in dimensions with so~e ~f the great fresh-water seas of Canada, the quantity of drift-timber brought down annually is enormous. " As the trees,'' says Dr. Richardson, '( retain their roots which are o:ten loaded with earth and stones, they readily' sink espe ... ~Ially when water-soaked, and, accumulating in the ;ddies JOrm sh oa Is , wh I ·c h u It 1· mately augment into islands. A thicke't of small w ·n I ows covers the new-formed island as soon as it appears above water, and their fibrous roots serve to bind the Vo: .. ~~~ount of the Arctic Regions, vol, ii. p. 193. t lb.·p. 202, R |
