PETRIFIED PLANTS AT LIEGE.

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liad sufficient power to carry them to the highest parts of thisdistrict, they would necessarily stop there, and travel no far-ther, since the force in the water diminishes with its depth.7. This view appears to be confirmed by calculation; for stoneis heavier than water in the proportion of about 2| to 1: butwhen placed in water, it loses a part of its weight equal to 1, sothat in this case, it only weighs to that element as 1| to 1; andstill less in salt water. When the bottom of the sea, therefore,is agitated, it follows that the deeper waters possess sufficientpower to transport weights hither and thither, although heavierthan water in the proportion of 1£ to 1: as is indeed proved bytorrents, which frequently tear away masses of stone, and over-throw walls of solid masonry. Dykes, though built of stone,are overthrown when the water rises three or four ells higherthan usual, owing to the power which it immediately gains bythe increase of depth, as I have myself known to occur inSweden a hundred times. Another proof is afforded by thepower of our atmosphere, which carries away bodies a thousandtimes heavier than itself, and conveys them to a great distance.Do we not often see heaps of sand whirled off in a storm for athousand paces ? Also dust, wood, bark, trees, and manyother bodies a thousand times heavier than the atmosphere?This appears to be owing both to the increased area of smallbodies, and to the weight of the atmosphere moving at thebottom, i.e. on the surface of the earth. In a similar mannerthe Ocean, in gales of wind, produces an irregularity, often ex-tending for miles, in its shoals and sand-banks, and likewiseat its own bottom. If then the atmosphere, though a thousandtimes lighter than water, can exert such a force on heavy bodies,as to transport them from place to place, what must have beenthe power of this mighty and ponderous ocean ? This gives ussome glimpse of the origin of mountains; provided the causeassigned is worthy to be accounted geometrical.

On the Petrified Plants found at Liege .

Although at the present day large collections have beenmade of different kinds of petrifactions, it may notwithstandingbe desirable to notice certain plants found in vast quantities