and stone implements of the aboriginal inhabitants of our island. (Wond. p. 47.)

In the extensive peat bogs of Ireland (Wond. p. 49.), large forest trees are often buried, together with the skeletons of the elk, deer, and other animals of the chase, and sometimes the bodies of the primitive hunters, wrapped in skins. In Belfast Lough, a bed of submarine peat is situated beneath the ordinary level of the waters, but is generally left bare at the ebb tides, Trunks and branches of trees, with vast quantities of hazel nuts, are imbedded in the peat; the whole being covered by layers of sand, shells, and blue clay, or silt.

In most cases the nut-shells of peat bogs are empty, the kernels having perished; but on the eastern side of this Lough, which is bounded by limestone rocks, the nuts contain calcareous spar, which in some examples fills up the cavity and assumes the form of the kernel, (see Plate III. fig. 7.) and in others forms a lining of delicate crystals (Plate V. fig. 6.). The pericarps, or shells, are entire, and in the state of common dried hard nuts; the water which deposited the calc-spar in their cavities, having left not a particle of mineral matter in the ligneous pericarp through which it filtered.

LIGNITE, (wood-stone,) BROWN COAL, or CANNEL COAL, are terms employed to designate certain varieties of carbonized wood, which still obviously present a ligneous structure; it may be designated

imperfect coal; for in its chemical properties it holds an intermediate place between peat and coal. It is generally deposited among the newer strata, and is found in the most recent as well as in the oldest tertiary formations; it is not unfrequent in some of the ancient secondary deposits, and may occur in the earliest sedimentary rocks which contain organic remains.

The newer deposits of brown or wood-coal, are commonly situated in depressions or basins, as if they had been produced by the submergence of woods and forests, beneath a swamp or morass. Specimens often exhibit the carbonized ligneous structure passing into a pure black coal, differing in no respect from true coal, except that it is less dense. One of the most instructive deposits of brown coal in England, is that of Bovey Heathfield, near Chudleigh in Devonshire, which is of considerable thickness and extent, and presents all the characters of a true coal-field; namely, beds of carbonized vegetables, alternating with clay and marl.

The Bovey coal is in the state of bituminized wood, the vascular tissue (which is coniferous in the specimens that have come under my notice) being very apparent. It is easily chipped or split, and it leaves a considerable quantity of white ashes after combustion. The layers of coal vary in thickness from one foot, to three feet; and there are eighteen or twenty in a depth of about 120 feet; this coal-field extends seven or eight miles. No

leaves or fruits have been found in the Boyey coalfield; bitumen has been observed both in the coal and in the intermediate clays. Calcareous spar, and iron pyrites, prevail in many of the strata. In some places this brown coal is covered by a bed of peat, in which trunks and cones of firs are imbedded. The whole series of strata appears to have been a lacustrine deposit; probably formed in a lake or bay, into whose basin rafts of pine forests were drifted by periodical land-floods (Org. Rem. I. p. 127.).

The brown-coal formations on the banks of the Rhine, present the same phenomena on a more extended scale, and complicated with changes induced by volcanic action (Wond. p. 269.). In Iceland, where at the present time woods are unknown, there are extensive deposits of lignite of a peculiar kind, which is termed surturbrand.

The beautiful substance called Jet, is a compact lignite, and the vascular tissue may be detected even in the most solid masses; when prepared in very thin slices, it appears of a rich brown colour by transmitted light, and the woody texture is visible to the naked eye..

Jet is found in great purity and abundance in the cliffs of alum-shale on the Yorkshire coast, which were celebrated in the early centuries for the production of this substance. At Whitby and Scarborough extensive manufactories of ornaments and trinkets of jet are established. The sandstone cliffs

near Whitby contain an impure or stony jet, termed anthracite. In the front of the cliff, on the northwest side of Haiburn Wyke, the stump of a tree was observed in an erect position, about three feet high, and fifteen inches in diameter; the roots were in a bed of shale, in the state of coarse jet, while the trunk, which extended into the sandstone, consisted in part of silicified wood, and in part of wood in a state of decay, with a sooty aspect.*

Thin seams and layers, and nodular masses, as well as regular coal-fields of lignite, occur in the tertiary formations. At Castle Hill, near Newhaven, in Sussex, (Wond. p. 225. Geol. S. E. p. 55.) a layer of lignite, a few inches thick, resembling the surturbrand of Iceland, is interposed between strata of red marl, in which are carbonized leaves of dicotyledonous trees.

At Alum Bay in the Isle of Wight, beds of lignite are seen between the vertical gravel and sand, of that interesting locality.

The Wealden formation contains, principally in its middle division of strata, thin layers of lignite, which alternate with finely laminated micaceous sandstones, marls, and clays, abounding in minute carbonized fragments of leaves, fresh-water shells, and crustacea. This series so remarkably exhibits

* Geological Survey of the Yorkshire Coast; by Rev. G. Young; 1828; p. 197..

all the features of a coal-field, that many years since extensive works were carried on in the expectation that coal might be obtained of suitable quality for economical purposes. The search was unsuccessful, bút the attempt deserves not the censure that was bestowed upon it, in the infancy of geological science (See Sir J. F. W. Herschel's Discourse on Nat. Phil.). Experience has since shown, that although the true coal-measures are only found beneath the saliferous formation, the production of good combustible bituminous coal is not necessarily restricted to any period or series of strata, but may occur wherever the local conditions were favourable to the complete bituminization of beds of vegetable matter. In fact, the productive coal-fields of Bückeburg, in Hanover, are situated in deposits of the Wealden epoch (Wond. p. 688.). A microscopical examination of the lignite of Tilgate Forest, has hitherto afforded me no trace of structure; from which it may be presumed, that this substance has not resulted from coniferæ, since their vascular tissue is easily detected in coal, but from plants possessing a less durable organization.

Many interesting facts relative to the carbonization of vegetables, came under my observation during my researches in the Wealden strata; and it is a subject of regret to me, that circumstances prevented my following up the investigation of those very imperfectly explored deposits. Small nodular portions of coal, in which no structure is apparent,