and sang again the song that Moses taught them, the psalms their kings and prophets had bequeathed. So should the corrupted world return to the God it has forsaken, and the knowledge of him be established in all the earth, and sin and Satan be expelled from it, this talent, and every other, will find the use for which it was intended-will be made to subserve the holiness as well as the happiness of man, and before all things the glory and worship of the Lord. How shall we think then of our so long misuse? Or if we should never see a time when the earth shall be the Lord's, and the fulness of beauty with which he filled it be recovered from corruption, should we not as individuals, restored ourselves, endeavour to restore every thing else to the holy purpose its first creation?

of

CONVERSATIONS ON GEOLOGY,

CONVERSATION XVI.

Shale-Iron-Stone-Fossils-Shells.

MAT. I have not looked upon the fire since, without recalling the subject of our late conversation; and I must confess Geology has become a very interesting subject to me, as correcting many false ideas I had formed of the things with which I supposed myself most familiar.

MRS. L.—I am glad to hear it. Having dismissed the Coal in our last conversation, we have to speak briefly to-day of its accompanying Strata-for the usefulness of this wonderful formation is not yet exhausted.

ANNE. You mentioned Shale among the substances that divide the Coal. I am not aware of having heard the word before.

MRS L.-Shale is a sort of soft Slate, composed of nearly the same materials as the Clay Slate of the Pri

mary Rocks. Occurring under various circumstances among the Secondary Rocks, it is usually called Shale. Dr. M'Culloch thus describes it. "Under the term

Shale are included all the Argillaceous Schistes of the Secondary Class, sometimes also known by the inconvenient and awkward name of Slate Clay. These have seldom been found occupying extensive tracts in nature, and it is even rare to find them in considerable beds. The Orkney Islands are, however, an exception to this general rule. They are commonly in the form of thin Strata, often of mere laminæ, alternating with the other rocks with which they are associated. Hence they are implied by Geologists, where they are not mentioned in any series, or formation; being as subordinate substances. They present, in this case, a striking analogy to the Argillaceous Schistes of the Primary Class, which often occur in a similar manner among the other rocks of that division. They are found in the lowest Red Sandstone under a great variety of characters; and of this, Arran presents a very striking example. Very commonly also, in this case, they resemble the Graywacke of the Primary Class so strongly, that they cannot be distinguished by their mineral characters; a circumstance already mentioned in treating of that rock. In some instances, as in the Orkney Islands, and on the north-west coast of Scotland, these beds occupy a space so considerable among the rocks with which they are associated, as to be a source of doubt to the Geologist; since under peculiar circumstances of exposure, and of limited access to the series, it may thus be impossible to distinguish them from the Primary Graywacke. In these cases, in fact, there sometimes appears to be an actual transition between the Primary and Secondary Classes; the appearance of such a transition being rendered more perfect by the conformable order of the two. Shale also forms a member of the various Sandstones which lie above the lowest, or Red Sandstone; occurring through the greater number of those with which we are acquainted,

and in some, very conspicuously. In these cases also, it is often very difficult to distinguish it from the finer Graywackes of the Primary series; while, in some instances, it is even easily confounded with Clay Slate, as formerly remarked, unless examined in conjunction with its geological connexions. It occurs in many of the Secondary Limestones, either alternating with the calcareous Strata in considerable beds, or forming thin laminæ, or else entering as a constituent with other substances, into some of the peculiar groups in which many of these are found. Shale is also associated with Coal. In this case, it either alternates with the Coal itself, or forms a component part of the peculiar series of which that substance is the most conspicuous 'member. Further, it is found among the Clays; some portions of these important deposits appearing to have been indurated into this form, while others have retained their loose, earthy character. The texture of all the Shales is more or less schistose (slaty), and many of them also break according to certain natural joints, by which they are divided in the beds. In other respects they present many different aspects, arising from the greater or less fineness of their materials, or the variety of substances which enter into their composition. They sometimes also contain larger fragments or nodules of the rocks, from the decomposition of which they have been formed. Lastly, they contain organic remains both vegetable and animal. In the Limestones, they are often the principal repository of the shells which appertain to these groups of beds. They are also the occasional repositories, like Marl and Coal, of the remains of vegetables. From analogous causes they are also often impregnated with bitumen, even in such excess, as to be imperfectly combustible." Fig. 1 is a specimen of Shale.

MAT.-Shale then, it appears, is the ruins of the Primary Slates, as Graywacke and Grit, with which it associates, are of the Granites, Marbles, &c.

MRS. L.-This is probably the case; with a mixture