the new town is a hollow, in which, tradition says, the river Sipparah formerly ran. It changed its course at the time the city was buried, and now runs to the westward *." The soil which covers Oujein is described as "being of an ash-grey colour, with minute specks of black sand +."

That the "shower of earth" which is reported to have "fallen from heaven," was produced by a volcanic eruption, we cannot doubt, although no information has been obtained respecting the site of the vent; and the nearest volcano of which we read, is that which was in eruption during the Cutch earthquake in 1819, at the distance of about thirty miles from Bhooi, the capital of Cutch, and at least three hundred geographical miles from Oujein.

Captain F. Dangerfield, who accompanied Sir John Malcolm in his late expedition into Central India, states that the river Nerbuddah, in Malwa, has its channel excavated through columnar basalt, on which rest beds of marl impregnated with salt. The upper of these beds is of a light colour, and from thirty to forty feet thick, and rests horizontally on the lower bed, which is of a reddish colour. Both appear from the description to be tuffs composed of the materials of volcanic ejections, and forming a covering from sixty to seventy feet deep overlying the basalt, which seems to resemble some of the currents of prismatic lava in Auvergne and the Vivarais. Near the middle of this tufaceous mass, and therefore at the depth of thirty feet or more from the surface, just where the two beds of tuff meet, Captain Dangerfield was shown, near the city of Mhysir, buried bricks and large earthen vessels, said to have belonged to the ancient city of Mhysir, destroyed by the catastrophe of Oujein ‡.

* Narrative of a Journey from Agra to Oujein, Asiatic Researches, vol. vi. p. 36. Asiatic Journal, vol. ix. p. 35.

Sir J. Malcolm's Cent. Ind.-Geol. of Malwa, by Captain F. Dangerfield, App. No. ii. pp. 324, 325.

CHAPTER XV.

Imbedding of organic remains in subaqueous deposits-Division of the subject— Phenomena relating to terrestrial animals and plants first considered-Wood sunk to a great depth in the sea instantly impregnated with salt-waterExperiments of Scoresby-Drift timber carried by the Mackenzie into Slave Lake and into the sea-Cause of the abundance of drift timber in this river-Floating trees in the Mississippi-In the Gulf stream-Immense quantity thrown upon the coast of Iceland, Spitzbergen, and Labrador-Imbedding of the remains of insects-of the remains of reptiles-Why the bones of birds are so rare in subaqueous deposits-Imbedding of terrestrial quadrupeds-Effects of a flood in the Solway Firth-Wild horses annually drowned in the savannahs of South America-Skeletons in recent shell marl-Drifting of mammiferous and other remains by tides and currents.

We have treated hitherto of the imbedding of organic remains in deposits formed upon the emerged land, and we shall next consider the including of the same in deposits formed under

water.

It will be convenient to divide this branch of our subject into three parts; considering first, the various modes whereby the relics of terrestrial species may be buried in subaqueous formations; secondly, the modes whereby the animals and plants inhabiting fresh-water may be so entombed; thirdly, the manner in which marine species may become preserved in

new strata.

The phenomena which we are now about to notice demand a fuller share of attention than those previously examined, since the deposits which originate upon the dry land are insignificant in thickness, superficial extent, and durability, when contrasted with those of subaqueous origin. At the same time, the study of the latter is beset with greater difficulties, for we are here concerned with the results of processes much more removed from the sphere of ordinary observation. There is, indeed, no circumstance, as we before remarked *, * Vol. i., p. 81.

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 element,—to that larger portion of the habitable globe, from which, 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-logged and sinks. The 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 lose 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 occasion 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 weight of the sunken boat which still remained attached to it. By means of harpoons and ropes the fish was prevented from sinking until it was released from the weight by connecting a rope to the lines of the attached boat, 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.

end to keep it from sinking. ship, the paint came off the wood in large sheets; and the planks, which were of wainscot, were as completely soaked in every pore as if they had lain at the bottom of the sea since the Flood! A wooden apparatus that accompanied the boat in its progress through the deep, consisting chiefly of a piece of thick deal, about fifteen inches square, happened to fall overboard, and, though it originally consisted of the lightest fir, sank in the water like a stone. The boat was rendered useless; even the wood of which it was built, on being offered to the cook for fuel, was tried and rejected as incombustible *."

"When it was hoisted into the

Captain Scoresby found that by sinking pieces of fir, elm, ash, &c., to the depth of four thousand and sometimes six thousand feet, they became impregnated with sea-water, and when drawn up again, after immersion for an hour, would no longer float. The effect of this impregnation was to increase the dimensions as well as the specific gravity of the wood, every solid inch having increased one-twentieth in size and twenty-one twenty-fifths in weight †.

When timber is drifted down by a river, it is often arrested by lakes, and becoming water-logged it may sink and be imbedded in lacustrine 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 accumulations of vegetable matter now in progress under both these

circumstances.

In Slave Lake in particular, which vies in dimensions with some of 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 often loaded with earth and stones, they readily sink, especially when water-soaked, and, accumulating in the eddies, form shoals, which ultimately augment into islands. A thicket of small willows covers the new-formed island as soon as it above water, and their fibrous roots serve to bind the † Ib. p. 202. R

appears

* Account of the Arctic Regions, vol. ii. p. 193. VOL. II.

whole firmly together. Sections of these islands are annually made by the river, assisted by the frost; and it is interesting to study the diversity of appearances they present according to their different ages. The trunks of the trees gradually decay until they are converted into a blackish brown substance resembling peat, but which still retains more or less of the fibrous structure of the wood; and layers of this often alternate with layers of clay and sand, the whole being penetrated, to the depth of four or five yards or more, by the long fibrous roots of the willows. A deposition of this kind, with the aid of a little infiltration of bituminous matter, would produce an excellent imitation of coal, with vegetable impressions of the willow roots. What appeared most remarkable was the horizontal slaty structure that the older alluvial banks presented, or the regular curve that the strata assumed from unequal subsidence.

"It was in the rivers only that we could observe sections of these deposits, but the same operation goes on on a much more magnificent scale in the lakes. A shoal of many miles in extent is formed on the south side of Athabasca Lake, by the drift-timber and vegetable debris brought down by the Elk River; and the Slave Lake itself must in process of time be filled up by the matters daily conveyed into it from SlaveRiver, Vast quantities of drift timber are buried under the sand at the mouth of the river, and enormous piles of it are accumulated on the shores of every part of the lake *.”

The banks of the Mackenzie display almost everywhere horizontal beds of wood coal, alternating with bituminous clay, gravel, sand, and friable sandstone; sections, in short, of such deposits as are now evidently forming at the bottom of the lakes which it traverses.

Notwithstanding the vast forests intercepted by the lakes, a still greater mass of drift-wood is found where the Mackenzie reaches the sea, in a latitude where no wood grows at present except a few stunted willows. At the mouths of the river the

*Dr. Richardson's Geognost. Obs. on Capt. Franklin's Polar Expedition.