both concurred to preserve that gloomy light which, to their untutored minds, inspired religious veneration and dread.

In even the most admired Gothic edifices, no regard seems to have been paid to the proportion between the length of the shaft of a column and its diameter: no rules can be deduced from the Gothic practice, as from that of the Greeks and Romans, to fix the proportions of the columns and its parts; neither are the intercolumniations determined. Examples of the widest difference in this respect are common, for instance in the nave of York cathedral and in the aisles of the conventual church of Newarkupon-Trent, both Gothic buildings deservedly admired but widely differing the one from the other, both in the proportion of the columns and in the intervals between.

1

THE

THE

MODERN PRECEPTOR.

CHAPTER XII.

OF GEOLOGY.

GEOLOGY is a term formed from two Greek words, signifying a discourse concerning the earth: it comprehends that part of the history of nature which treats of the structure of the earth, of the arrangement of its component materials, and of the changes which these materials have undergone. By some modern naturlists the term geognosy has been substituted for geology: but the latter seems to merit the preference. Geology may be divided into two branches, the descriptive, containing a general account of the materials of the globe of the earth, and the speculative, which is confined to the theories by which attempts have been made to explain the manner in which the present appearances of the earth have been produced.

The study of geology is of the highest importance in many respects. By it the naturalist is made acquainted with a very extensive department of natural productions; to him the minerals composing the internal strata of the globe and the mountains which soar above its surface are objects

VOL. II.

3 E

objects peculiarly interesting. To the miner this study is of the greatest usc, as it instructs him in the nature and arrangements of the various substances in the bowels of the earth, by which he is led from the discovery of one substance to direct his operations for the discovery of some other, the object of his research. By an acquaintance with geology the landed proprietor may be guarded against the artifices or the ignorance of a projector, and thus prevented from embarking in expensive and precarious enterprises, which have but too frequently ended in disappointment and ruin. But the study of geology possesses still a higher advantage: nothing has more contributed to demonstrate the truth of the sacred writings, and to clear up many difficult passages in them, than the discoveries lately made in the structure and arrangement of the earth. The original state of the globe is so intimately connected with that which it at present exhibits, that we cannot properly understand the latter without a reference to the former: and recent experience has shown that the obscurity in which the philo sophical knowledge of this subject was involved, has been highly favourable to those systems of infidelity and atheism which in the last age were but too prevalent. Of this obscurity much has been removed; and the investigations of Whitehurst, Werner, Kirwan, Howard, and some other geologists, by proving that the supposition of a deluge is the only hypothesis on which we can account for the present state and appearances of our globe, have contributed as much to the advancement of rational religion as of philoso phical knowledge.

The study of geology, like other parts of natural history,, can be pursued with but little advantage in the closet: the student must examine the sloping sides of hilis, the beds of rivers, the interior of caverns and mines, the recesses of ravines, and the utmost summits of mountains, before he can obtain the knowledge requisite to form a skilful and philosophical

geologist.

geologist. While employed in these personal observations, however, he ought carefully to study the works of the best writers on the subject, comparing the facts stated by them. with those he has himself observed. The writings on geology may be separated into two sorts, the first containing those which give a systematic account of the whole or of some portion of the whole science, such as Bergmen's Physical Geography, Kirwan's Geological Essays, Delametherie's Theorie de la Terre, Werner's works, &c. &c.; the second sort comprehending geological descriptions of particular countries, such as Born's Travels in Hungary, Ferber's Travels in Italy, Saussure's Travels in the Alps, Pallas's Travels in the Russian Empire, Tar's Voyages Metallurgiques, Travels in England and Scotland by Faujas de St. Fond, &c. &c.

The materials of which the general body of our globe is composed are variously distributed in various parts: in some places they form irregular blocks or masses, buried below the surface, or elevated to different heights above it. In most places, however, these materials are arranged in a more regular way, those of the same kind being collected into extensive masses lying in strata or layers, above or below a similar mass of another sort; or these alternate with each other to a considerable depth. At one time these layers or strata are found arranged in a direction parallel to the horizon, at other times they are placed vertically or perpendicular to the horizon, as if what had originally been laid horizontally had been lifted up and set on its edge. But it is more common to find the strata arranged in a direction between the horizontal and the perpendicular, or inclined at different angles to the horizon, in which case they are said. to dip.

The uppermost layer or stratum is in most places covered with mold, evidently formed from the decomposition of substances once endowed with organic or animal and

vegetable life. In many parts this mold extends to a very considerable depth, constituting what is called the soil: in other places the mold is barely sufficient to form a coating for the inferior strata; and in some places it is entirely wanting.

Sometimes the strata are continued in a regular arrangement, preserving the same degree of inclination to a considerable extent; but more commonly they appear separated into parts, as if they had been broken asunder, and the several parts are often raised above or sunk below the corresponding portions to which they were originally united. The separations, which are usually in a perpendicular direction, are sometimes filled with fragments of the adjacent broken strata, but for the most part they contain mineral or metallic substances of a very different nature.

When these separations, cracks, or fissures are filled up with broken fragments of the adjacent strata, they frequently become the beds of rivers; when filled with a solid strong substance they form what the miners call a dyke; if a mass of mineral or metallic substance fill the fissure, or be insinuated between the strata, it forms what is called a vein; and these veins frequently spread in branches between the strata in various directions.

If the country in which the strata lie run in a waving direction of gentle hill and dale, the different substances usually preserve the same waving direction, keeping nearly parallel the one with the other. In those places where no remarkable dislocation of the strata has taken place, their distribution is in general regular, certain materials lying above or below certain others in an uniform manner.

From the accumulated observations of geologists all these materials may be arranged under two heads: the first class contains all those substances which are found more or less connected with the remains of organized bodies, (animals and vegetables), such as the bones, teeth, shell;

of