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Thus we find corals, originally calcareous, in which not only the general shape, but also the minute and complicated internal organisation is retained in flint. Such a process of petrifaction is still more remarkably exhibited in fossil wood, in which we often perceive not only the rings of annual growth, but all the minute vessels and medullary rays.
Therefore, with regard to the composition of mineral coal, the theory is this. That inflammable, vegetable, and animal substances, in a subtilised state, had subsided in the sea, being mixed more or less with argillaceous, calcareous, and other earthy substances in an impalpable state.
Near Nice large castings abound in extraordinary numbers, so that 5 or 6 were often found within the space of a square foot. They consist of fine, pale-coloured earth, containing calcareous matter, which after having passed through the bodies of worms and being dried, coheres with considerable force.
To see the evidence of marble, a body that is solid, having been formed of loose materials collected at the bottom of the sea, is not always easy, although it may be made abundantly plain; and to be convinced that this calcareous stone, which calcines so easily in our fires, should have been brought into fusion by subterraneous heat, without suffering calcination, must require a chain of reasoning which every one is not able to attain . But when fire bursts forth from the bottom of the sea, and when the land is heaved up and down, so as to demolish cities in an instant, and split asunder rocks and solid mountains, there is nobody but must see in this a power, which may be sufficient to accomplish every view of nature in erecting land, as it is situated in the place most advantageous for that purpose.
In attempting to explain the process of petrifaction in such cases, we may first assume that strata are very generally permeated by water charged with minute portions of calcareous, siliceous, and other earths in solution. In what manner they become so impregnated will be afterwards considered.
As the calcareous envelope becomes opaque and solid, the animal within loses its transparent delicacy, and coincidentally the apex of the capsule opens slightly. In the meantime the fluid contents have disappeared, as if the animal had resulted from its solidification.
How faint an idea does this exclamation of the poet convey of the real wonders of nature! for here we discover proofs that the calcareous and siliceous dust of which hills are composed has not only been once alive, but almost every particle, albeit invisible to the naked eye, still retains the organic structure which, at periods of time incalculably remote, was impressed upon it by the powers of life.
Oswell, with his wonted generous feelings, volunteered, on the spot, to go down to the Cape and bring up a boat, we resolved to make our way south again. Coming down the Zouga, we had now time to look at its banks. These are very beautiful, resembling closely many parts of the River Clyde above Glasgow. The formation is soft calcareous tufa, such as forms the bottom of all this basin.
It was composed, where I could examine it, of the calcareous breccias of the sea-coast. Marly and calcareous beds alternate with other beds containing grains of quartz.
The cavity within the coated part of the pebble is filled up without vacuity, first, with colourless siliceous crystals; secondly, with fuliginous crystals; and, lastly, with white or colourless calcareous spar. But between the spar and crystals there are many sphericles, seemingly of iron, half sunk into each of these two different substances.
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