miles in circumference. No less than 57 species of ferns, some few of them arborescent, have been already discovered in this country; and what is remarkable, one tree-fern ranges in this country as far south as the 46th degree, south latitude. There are no indigenous mammalia except one rat, and a species of bat; few reptiles, and none of large size; so that we may anticipate a total absence of the bones of land quadrupeds, and a scarcity of those of reptiles, in the modern estuary and lacustrine deposits of this region. That there are lacustrine strata now in progress is certain, since one lake, called Rotorua, in the interior of the northern island, is said to be 40 miles long, and receives the waters of many small rivers and

The minor repetitions of alternate fresh and saltwater strata in the Coal, have been ascribed to such changes as may annually occur near the mouths of rivers; but when shale and grit, containing coal and freshwater shells, are covered by large masses of coralline rock, and these again by other Coal-measures, we must suppose great movements of elevation and subsidence, like those by which I endeavoured to explain, in Chapters XVI. and XVIII., the superposition of the Cretaceous group to the Wealden, or the alterna

* Account of New Zealand, published for New Zealand Association.

tions of argillaceous and calcareous rocks in the Oolite. In adopting such views, we must suppose the lapse of vast periods of time; as the thickness of the Coal strata, in some parts of England, independently of the Mountain limestone, has been estimated at 3000 feet. Besides, we can by no means presume that all coal-fields were in progress at once, much less that, in the same field, each mass of strata which is parallel, or occupies a corresponding level, was formed simultaneously. It is far more consistent with analogy to suppose that rivers filled up first one part of a fiord, gulf, or bay, nearest the land, and then another; so that the sea was gradually excluded from certain spaces which it previously occupied. This is doubtless the cause why the coal-bearing strata are generally uppermost, and the Mountain limestone the lowest part of each series; and why, in certain districts in the S. W. of England, the Mountain limestone suddenly thins out, so that coal-shales and grit rest immediately upon older and unconformable rocks.

Erect position of fossil trees in the Coal strata.— A great number of the fossil trees of the Coal are in a position either oblique or perpendicular to the planes of stratification. This singular fact is observed on the Continent as well as in England, and merits great attention, not only as opening a curious field for speculation, but because it has

furnished a popular argument to some writers who desire to prove the earth's crust to be no more than 5000 or 6000 years old. The fact did not escape the notice of Werner, who conceived that the trees must have lived on the spots where they are now found fossil; and this hypothesis was defended by M. Alexandre Brongniart, in the account given by him, in 1821, of the coal-mine of Treuil, at St. Etienne, near Lyons.* (Fig. 270.) Fig. 270.

Section showing the erect position of fossil trees in coal-sandstone at
St. Etienne. (Alex. Brongniart.)

In this mine, horizontal Coal strata are traversed by vertical trunks of Monocotyledonous vegetables

resembling bamboos, or large Equiseta. These beds are represented in the above figure (270.), and are from 10 to 13 feet in height, consisting of micaceous sandstone, distinctly stratified, and passing into the slaty structure. Since the con

solidation of the stone, there has been here and there a sliding movement, which has broken the continuity of the stems, throwing the upper parts of them on one side, so that they are often not continuous with the lower.

Now, had these trees, as some geologists contend, once formed part of a submerged forest like that of Portland, before described (see p. 353.), all the roots would have been in the same stratum, or would have been confined to certain levels, and not scattered irregularly through the mass. Besides, when the stems have any roots attached to them, which happens but rarely, they are imbedded in sandstone precisely similar to that in which the trunks are inclosed, there being no soil of different composition like the Portland dirtbed,—no line of demarcation, however slight, between the supposed ancient surface of dry land and the sediment now enveloping the trees.

Some may, perhaps, think it superfluous to advance such objections to M. Brongniart's theory, since Dr. Buckland has informed us that, when he visited these same quarries of Treuil in 1826, he saw so many trunks in an inclined posture, that

*

the occasional verticality of others might be accidental. Nevertheless, the possibility of so many of them having remained in an upright posture demands explanation; and there are analogous cases on record respecting similar fossils in Great Britain of a still more extraordinary nature.

In a colliery near Newcastle, say the authors of the Fossil Flora, a great number of Sigillarias were placed in the rock as if they had retained the position in which they grew. Not less than 30, some of them 4 or 5 feet in diameter, were visible, within an area of 50 yards square, the interior being sandstone, and the bark having been converted into coal. The roots of one individual were found imbedded in shale; and the trunk, after maintaining a perpendicular course and circular form, for the height of about 10 feet, was then bent over so as to become horizontal. Here it was distended laterally, and flattened so as to be only one inch thick, the flutings being comparatively distinct. Such vertical stems are familiar to our miners, under the name of coalpipes. One of them, 72 feet in length, was discovered, in 1829, near Gosforth, about five miles from Newcastle, in coal-grit, the strata of which it penetrated. The exterior of the trunk was marked at intervals with knots, indicating the

* Bridgew. Treat., p. 471.

+ Lindley and Hutton, Foss. Flo., part 6. p. 150.