in

little over, leaving the division which now exists between them This is rendered obvious by the first of the rough outlines pen and ink which I have annexed, the correspondence of the forms being there distinctly seen exactly as they appear in nature, and likewise proving, by the spherical form of the frac ture, the globular structure already mentioned in the left hand portion.

The stone is excessively hard, except where it has begun to disintegrate; even with a very heavy hammer, it was not without great labour that I succeeded in obtaining specimens of a considerable size. I send some of the disintegrated portions, which are from the concentric lamellæ of the western half of the boulder. You will be the fittest judge of the precise nature of the stone (which appears to be greenstone, pretty highly crystallized, and containing a little iron pyrites), and what may be the most probable site of its parent rock. To one fact relating to the theory of boulders, and the period at which they were deposited, I would call your attention, from the peculiar situation in which this mass lies, and of which, in the sketches, I have attempted to give some idea. Being placed upon the actual declivity of a small but steep ravine, it seems physically impossible that, had that valley existed at the time of its journey, it should not have been precipitated to the bottom of it. If it came from the last, it is not credible that it should have crossed the channel of the streamlet, and ascended half way up the western bank; and it is equally beyond explanation that, by any power short of a miracle, had it come from the west, the course of so enormous a mass (the weight of which I shall endeavour to estimate), should have come to a stand under the influence of the tremendous impetus, of whatever kind, by which it was moved, in the middle of a short and steep descent of this description. I therefore consider the induction undeniable, that the excavation of the valley must have taken place subsequently to the deposition of this boulder.

In order to form a rough estimate of the size of the fragment, after an attentive inspection by the eye, I conceived the western portion, as far as it is uncovered, to be a semicylinder seven feet long, and three and a half in diameter; and the eastern, a parallelopiped, having a mean of six feet, four and a half feet, and

two and a half feet, for its three dimensions. From these assumptions, which must be considered merely as rough approximations, I computed the former fragment to contain about 33 cubic feet, and the later 67. Allowing a half of the bulk of the former for the portion buried, we shall have about 117 cubic feet for the whole.

To gain some idea of the weight of the mass, I took, with great accuracy, the specific gravity of a fresh fractured portion, which I found to be 2.90*; whence the weight of a cubic foot will be 181 fb., and the whole mass near 200 cwt., or about 10 tons. Its enormous momentum may therefore be conceived, when it was transported to its present situation from a distance certainly of some miles. From the spontaneous decomposition of the greenstone, it is not easy to determine whether it suffered much from attrition in its transportation; but I am disposed to think it has not, from the angular form of the eastern fragment, which now exhibits scarcely the least tendency to disintegration, forming a striking contrast to the other portion with which it has been so closely united.

The argument of the excavation of valleys subsequent to the deposition of boulders might, I believe, be inferred from nume⚫rous cases, though this is the strongest I have met with. They are often placed in such insulated situations in mountainous countries as to intimate the degradation of the surrounding soil.

I fear I may have extended my remarks beyond the importance of the subject. But as you were very particular in your inquiries when we last met, I collected such observations as you might consider interesting.

Notice of Earthquakes on the Mississippi. By Mr FLINT

FROM all the accounts, corrected one by another, and compared with the very imperfect narratives that were published, says Mr Flint, I infer that the shock of these earthquakes, in the immediate vicinity of the centre of their course, must have equalled, in their terrible heavings of the earth, any thing of the kind that has been recorded. I do not believe that the public have ever yet had any adequate idea of the violence of the concussions. We are accustomed to measure this, by the buildings overturned, and the mortality that results. Here the country was thinly settled. The houses fortunately were frail and of logs, the most difficult to overturn that could be constructed. Yet, as it was, whole tracts were plunged into the bed of the river. The grave-yard at New Madrid, with all its sleeping tenants, was precipitated into the bed of the stream. Most of the houses were thrown down. Large lakes, of twenty miles in extent, were made in an hour; other lakes were drained. The whole country to the mouth of the Ohio, in one direction, and to the St Francis in the other, including a front of three hundred miles, was convulsed to such a degree, as to create lakes and islands, the number of which is not yet known, to cover a tract of many miles in extent near the Little Prairie, with water three or four feet deep; and, when the water disappeared, a stratum of sand, of the same thickness, was left in its place. The trees split in the midst, lashed one with another, and are still visible over great tracts of country, inclining in every direction, and at every angle to the earth and to the horizon.

They described the undulations of the earth as resembling waves, increasing in elevation as they advanced; and, when they had attained a certain fearful height, the earth would burst, and vast volumes of water and sand and pitcoal were discharged, as high as the tops of the trees. I have seen a hundred of these chasms, which remained fearfully deep, although in a very tender alluvial soil, and after a lapse of seven years. Whole districts were covered with white sand, so as to become uninhabitable.

The water at first covered the whole country, particularly at the Little Prairie; and it must have been indeed a scene of horror, in these deep forests, and in the gloom of the darkest night, and by wading in the water to the middle, to flee from these concussions, which were occurring every few hours, with a noise equally terrible to the beasts and birds as to men. The birds themselves lost all power and disposition to fly, and retreated to the bosoms of men, their fellow-sufferers in this scene of convulsion. A few persons sunk in these chasms, and were providentially extricated. One person died of fright; one perished miserably on an island, which retained its original level, in the midst of a wide lake created by the earthquake. The hat and clothes of this man were found. A number perished, who sunk with their boats in the river. A bursting of the earth, just below the village of New Madrid, arrested this mighty stream in its course, and caused a reflux of its waves, by which, in a little time, a great number of boats were swept by the ascending current into the mouth of the Bayou, carried out and left upon the dry land, when the accumulating waters of the river had again cleared their current. There were a great number of severe shocks, but two series of concussions were particularly terrible, far more so than the rest. They remark, that the shocks were clearly distinguishable into two classes; those in which the motion was horizontal, and those in which it was perpendicular. The latter were attended by the explosions and the terrible mixture of noises that preceded and accompanied the earthquakes in a louder degree, but were by no means so desolating and destructive as the other. When they were felt, the houses crumbled, the trees waved together, the ground sunk, and all the destructive phenomena were more conspicuous. In the intervals of the earthquakes there was one evening, and that a brilliant and cloudless one, in which the western sky was a continued glare of vivid flashes of lightning, and repeated peals of subterranean thunder seemed to proceed, as the flashes did, from below the horizon. They remark that this night, so conspicuous for subterranean thunder, was the same period in which the fatal earthquakes at Caraccas occurred, and they seem to suppose these flashes and that event parts of the same scene.

The people, without exception, were unlettered backwoodsmen, of the class least addicted to reasoning. And it is remarkable how ingeniously and conclusively they reasoned from apprehension sharpened by fear. They remarked, that the chasms in the earth were in direction from south-west to northeast, and they were of an extent to swallow up, not only men but houses, and these chasms occurred frequently within intervals of half a mile. They felled the tallest trees at right angles with the chasms, and stationed themselves upon the felled trees. By this invention all were saved; for the chasms occurred more than once under these trees.

Silliman's Journal, January 1829.

On the Circumstances which appear to have accompanied the Deposition of the Tertiary Formations. In a Letter addressed to M. ADOLPHE BRONGNIART, by M. MARCEL DE SERRES.

THE observations recently made by M. Elie de Beaumont, on the fossil vegetables of the anthracite or glance coal deposites of the Alps, and the notes which you have added to them, appear to me so important, and seem to coincide so well with the facts which I have observed in the South of France, that they induce me to submit to you the following reflections, even before publishing the facts on which they are founded :—

You observe, and, as it seems to me, with perfect reason, that although, from the identity, or extreme similarity of the vegetables of the coal formation, in all parts of the globe, it is probable that the same kind of vegetation existed over the whole earth at the period when that combustible was deposited, it ought not to be inferred from this, that the same circumstance existed at the periods when the lias formation, the oolites, the chalk, or the Paris formations, were deposited, and that the vegetation was then the same over all parts of the globe.

I agree with you in thinking, that, in proportion as the earth became covered with a greater number of vegetables, and was inhabited by a greater variety of animal species, it tended more and more towards the settled state at which it has now arrived,