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Lignite, or brown coal, as it is also termed, as before stated, seems to be only a peat in a more bituminous state. It occurs in rocks chiefly of tertiary origin. A great number of lignites preserve their woody structures, whence their name. Jet is but the same in a more advanced state, and more compact: it is found in the Isle of Skye and at Whitby. On the banks of the Seine, in France, there is a thick bed of brown coal, in which whole trunks of trees are well preserved. In the environs of Cologne an earthy variety occurs, which exists in very extensive and thick beds, in which fossil trunks of trees, many of them belonging to palm species, are found imbedded. The greater part of our extensive coal beds have been formed somewhat in this manner. The ancient vegetation has grown in its rank luxuriance, and again decayed, unbeheld by the eye of man! yet not the less surely consigned to nature's vast coal cellars, there to exist, after having gone through its appointed changes, until required by that prodigal son of nature-man.

Doubtless, also, the drift theory will explain the mode of deposit in which many coal beds occur; the English coal fields seem to have been tolerably regular in their depositions-the Scottish, on the contrary, give evidence of having been deposited in basins, the site of ancient lakes or estuaries. There are processes now going on, which explain, in a great measure, the mode of this deposit (although these facts do not free the theory in the least, from the forementioned objections in general): the Mississippi, which passes through a country, thickly set with primeval forests, is often, after a storm, laden with trunks, and branches of trees; these are carried down the river, until arrested in their course, where they form rafts, often of considerable size; one was thus formed on an arm of the Mississippi, in 1816. The drifted trees had been collected about thirty-eight years previously, and had formed a continuous raft, no less than ten miles long, 220 yards wide, and eight feet deep; this was finally covered by a thick growth of bushes and underwood, the whole rising and falling with the water. It went on increasing until 1835, when the government ordered it to be cleared away. Here we have also a fact which illustrates the method of the drift theory, and at least substantiates its possibility.

The ancient flora, which, by its growth and decay, has formed our coal beds, was most singular, and quite characteristic of the formation. A short time ago we spoke of a seam of coal worked

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in the Yorkshire oolite; but, to the keen eye of a geologist, the impressions of the vegetation upon the shales point to a different era to that of the true coal measures, as the time of their deposition. In the coal formation of Great Britain about 900 species of fossil plants are known altogether, and of these 140 species are fossil ferns. The fossil ferns comprise the genera, Neuropteris, Sphenopteris, Pecopteris, &c. The Neuropteris is distinguished from the other genera by the mid-rib of the leaf, which anastomoses, or runs into the veins; the leaf is also contracted at the base. There are 28 species found. The mid-rib of the Pecopteris is continued to the apex of the leaf, and the leaf is often attached by the whole of its base to its stem. About 60 species are known. Sphenopteris, or wedge-shaped leaf, may readily be distinguished from the rest of the fossil plants by the leaflet being often divided and cleft; the leaflets are also contracted at their base :-of species, about 28 exist. The Asterophyllites, or stellar leafed fern, has its leaves of a wedge-shape, and arranged round its stem like the fancied rays of a star, whence its name; the mid-rib of the leaf is single, and the end often blunt: 12 species of this fossil are known. The Cyclopteris, or round leafed fern, had no distinct mid-rib, but the veins radiate from the base to the outer edge: four species of this plant are known. These are the chief, and the common genera of ferns met with in the carboniferous rocks. It is rather singular, but nevertheless true, that the fossil species of ferns decrease in number after the coal rocks, as we ascend upwards in the geological series. The other plants met with in the coal measures, are the following. The Calamite: this was a succulent tree, which often grew to the height of forty or fifty feet; its appearance was not much unlike the diminutive "mare's tail" (Equisetum) of our ponds and ditches; its stem was jointed like a reed, whence its name; it was also marked by perpendicular stripes or flutings; the breadth of these trees range from two or three feet to half-an-inch. The fructification took place at its apex; some specimens of this fossil, show it in this state, so well have they been preserved. Whoever has turned over the shales of any coal mine, must have noticed on their surfaces, diamond-shaped markings, most regularly pitted, this is the Lepidodendron, or scaly tree, as its name implies; the diamond-shaped scars are supposed to be the markings left by the fallen leaflet. It is an extinct form of vegetation, the nearest allied plant to it now existing, being the club moss; the largest species

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in the Yorkshire oolite; but, to the keen eye of a geologist, the
impressions of the vegetation upon the shales point to a different
era to that of the true coal measures, as the time of their deposition.
In the coal formation of Great Britain about 900 species of fossil
plants are known altogether, and of these 140 species are fossil
ferns. The fossil ferns comprise the genera, Neuropteris,
Sphenopteris, Pecopteris, &c. The Neuropteris is distinguished
from the other genera by the mid-rib of the leaf, which anastomoses,
or runs into the veins; the leaf is also contracted at the base. There
are 28 species found. The mid-rib of the Pecopteris is continued
to the apex of the leaf, and the leaf is often attached by the whole
of its base to its stem. About 60 species are known.
Sphenopteris, or wedge-shaped leaf, may readily be distinguished
from the rest of the fossil plants by the leaflet being often divided
and cleft; the leaflets are also contracted at their base :-of species,
about 28 exist. The Asterophyllites, or stellar leafed fern, has its
leaves of a wedge-shape, and arranged round its stem like the
fancied rays of a star, whence its name; the mid-rib of the leaf is
single, and the end often blunt: 12 species of this fossil are known.
The Cyclopteris, or round leafed fern, had no distinct mid-rib, but
the veins radiate from the base to the outer edge: four species of
this plant are known. These are the chief, and the common genera
of ferns met with in the carboniferous rocks. It is rather singular,
but nevertheless true, that the fossil species of ferns decrease in
number after the coal rocks, as we ascend upwards in the geological
series. The other plants met with in the coal measures, are the
following. The Calamite: this was a succulent tree, which often
grew to the height of forty or fifty feet; its appearance was not
much unlike the diminutive "mare's tail" (Equisetum) of our ponds
and ditches; its stem was jointed like a reed, whence its name; it
was also marked by perpendicular stripes or flutings; the breadth
of these trees range from two or three feet to half-inch. The
fructification took place at its apex; some speci
this fossil,

show it in this state, so well have they
ever has turned over the shales of any co
on their surfaces, diamond-shaped ma
this is the Lepidodendron, or scaly
diamond-shaped scars are suppo
fallen leaflet. It is an extinct
plant to it now existing, bein

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