of Clay or other substances that have floated with them, and been deposited and hardened into the same mass. Another substance which very often atttends the Coal. formations, is Argillaceous Iron-stone, both in layers and nodules; and although a poor ore of Iron, very seldom yielding more than thirty per cent. of metal, it becomes, from its associating with Coal and Limestone, (substances required for its reduction,) a most important natural product; it is the main source of the enormous quantities of Iron manufactured in this country; and the history of the various difficulties which have been surmounted in completing the processes of its reduction, presents an unrivalled picture of skill, ingenuity, and perseverance." I shall not speak more particularly of Iron-stone now-it will occur again. The argillaceous Iron-stone here spoken of, is, as its name implies, a mixture of Clay, Argil, and Iron-sand, of which we shall say more hereafter. For this the mines, exhausted of their Coal, are sometimes dug again-the walls, and roofs, and divisions of the Coal-beds containing layers or nodules of iron-stone; from which, by a laborious process of burning away the dross, one of our most valuable commodities is produced. It now only remains that I show you some of the Fossils of this valuable Strata.

ANNA. That is a part of our study that I feel particularly curious about. It unfolds facts and circumstances so mysterious.

MRS. L.-I have adopted this method of producing specimens of Fossils with those of the earths that contain them, in order to introduce you to this study, and make you familiar with the terms of it; the frequent introduction of which, in Geological works, without explanation, renders them obscure to the uninformed reader. The Fossils contained in these Strata, besides the vegetables of which I have given you one specimen, and of which Fig. 2 is another, being the impressions of the exterior bark of some unknown vegetable, called by Fossilists, Phytolithus Cancellatus, are shells of different

forms. And here perhaps I had better explain to you that shells in the fossil, as well as the recent kingdom, are called Univalved, Bivalved, or Multivalved, according as they are formed of a single shell, two shells, or more. Among the Fossils of the Sandstone and Coal Strata, there are specimens both of the Univalve and Bivalve Shells. Of the former are the Ammonites, which I have already shewn you in Plate 11. Another is the Orthocera, or Orthoceratites, Fig. 3-Plate 16. Conchologists would call this a Univalve, because the shell is but one, and multilocular, because the inside is divided into many chambers, by projections of the shell, called Septa. Fig. 4, is a Bivalve, termed Mytilus; it is also described as Equivalve, because both shells are alike. Another Bivalve, is the Unio, Fig. 5, and there are others of nearly similar construction. These remains of the living things of other days, have given rise to much conjecture and enquiry respecting the element they inhabited, some being asserted to be the inhabitants of salt water, and others of fresh water. But I confess I am not satisfied with any of the arguments I have read in proof of this assertion. In the above specimens, the Ammonites, Orthocera, and others, are known to live in salt water: the Unio is said to live in fresh water only, but this seems difficult to prove. If it should be so, it would not be difficult to imagine, in any great convulsion, a mixture of the two; but it becomes very extraordinary, when we find they are not intermixed, but laid separately in successive, and often alternating beds: of which we shall speak more hereafter.

MAT.-I apprehend we are now advancing very near the surface of our globe, are we not?

MRS. L.-You forget that you do not necessarily. advance nearer the exterior of the globe than you began; for the lowest, remember, is often the highest. In fact, the Alluvial deposits, which are the latest deposition, occupy the valleys, and low grounds only; while the first-formed substances claim the elevations. To

proceed, "leaving the districts of Red Sandstone, and Red Marle, we observe a change in the general aspect of the country. There are no steep or abrupt precipices; the hills assume a more picturesque and luxuriant character, and the rugged features of Primary country, are here softened down into gentle slopes, and verdant plains. The rocks which now occur, are chiefly varieties of Limestone and Sandstone, particularly prolific in organic remains; among which we discern a number of species, of which no living semblance is now in existence. Corals, Zoophites, Ammonites, Belemites, Nautili, and a variety of other fossil remains, are found in the Argillaceous Limestones, which succeed in position to the Red Sandstone, and which are often called White and Blue Lias Limestone. The coast of Dorsetshire, between Weymouth and Lyme, presents a very interesting section of these Strața; and their continuation through the country, is well entitled to the notice of the Geologist. They decompose into Marl, and furnish an ingredient in the best water cements. Sometimes they are are of a peculiar colour, and contain Magnesia, when the fossil remains are less frequent."

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MAT.-I am disposed to stop you for an explanation of all these new terms.

MRS. L.-The Ammonites I have shown you-Corals you know-Zoophites are of the Sponge tribe-Fig. 6, is a Spirifer-Fig. 7, a Belemnite.

DESCRIPTION OF BRITISH TREES.

No. XVI.

Ash Tree

Fraxinus.

THE Common Ash Tree, Fraxinus Excelsior, grows naturally in most parts of England, and is of great value as timber.

"The timber of the Ash (the Oak only excepted) serves for the greater variety of uses of any tree in the forest. Though a handsome