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THE

POPULAR EDUCATOR.

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AND LITHOLOGY-THE SOLAR SYSTEM, ETC. ETC.

THE derivation of the word Geology (yn [ghee], the earth, and Aéyos [logos], a discourse, or a reasoning) indicates the main direction of the science. It confines its attention to a description of the solid crust of the earth, and to the elucidation of those forces and causes which have produced the changes the surface of our planet has undergone. To aid him in his investigation, the geologist needs the aid of the botanist, the zoologist, the chemist, the mineralogist, the physicist, and even of the mathematician. Although the subject looks formidable to the general reader, it is not only fraught with the deepest interest, but by far its greatest part may be traversed by common sense. Moreover, its study commends itself to all, since it requires no expensive apparatus, nor yet a preparation which all other sciences demand ere the student can enter on their practice. Young and old, gifted with observation, may at once become practical geologists; and by never passing a stone-heap without an examination, or never leaving a quarry or gravel-pit unsearched, they will soon lay the foundation of a geological cabinet, and be efficient labourers in the extension of geological research.

Every generation of our race has produced men of inquiring minds, and it is but natural that such men should turn their research to discover the origin of the world we inhabit, especially in the early times when but few channels were opened along which they were invited to expend the natural vigour of their intellect; hence, in the earliest records of eastern nations we find theories which attempt to account for the existence of our earth-these it is unnecessary to dwell upon.

It is evident that the only sound mode of procedure is to collect all the information which observation of the various existing phenomena of nature can give; to search the crust of the earth for any facts which the rocks, their position, their character, their fossil contents, can afford; to notice the arrangement of continents and seas, the position and directions of mountain chains, etc., and from these letters of the geological alphabet to spell out the history of our globe.

The history of the progress of geology, like that of any other science, can furnish many instances of theories built up withcat any facts for foundations; but as patient research gradualy amassed information, these erroneous suppositions were atnadoned, and geologists have, from so many warnings, become extremely careful of hazarding opinions. The experiences by which we have been taught not to speculate, though interesting and instructive, we cannot record in these pages, as our limited space requires us to attend to facts and the deductions which may be reasonably drawn from them.

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The division of the subject we propose is the following:1. Physical Geology-that is, the geological agencies which have worked the various changes in the surface of our planet, both as to their present existence and as to the traces of their power which the rocks reveal.

2. The Geological Systems.-As we pass through these, we shall enumerate the fossils the rocks contain, the history of the animal and vegetable life of our globe, and the localities in which the members of these systems appear.

3. Mineralogy and Lithology.-In our last division we hope to describe the composition of the various kinds of rocks, as well as the physical and chemical properties of the minerals they contain.

Before we enter upon the immediate province of geology, it vai be well to consider our position in the universe, and someat of the character of our world as a globe, noticing the most

VOL. III.

plausible of the theories yet produced to account for the construction of our system, and therefore of our earth.

The solar system, of which we are one of the members, consists of the sun and eight planets-four of which are very much larger than the earth-and a number of very small planets, called asteroids, which revolve in the space separating the four exterior and larger planets from the interior and smaller ones. The position of the earth is the third from the sun. The earth is accompanied by a moon, which is not the case with any of the other interior planets, whilst the exterior planets are all attended by satellitesSaturn and Uranus by eight, Jupiter by four. All these bodies revolve round the sun in the same direction, and all move within a narrow belt. The exterior planets are much lighter than the interior. If the density of water be taken as 1, the density of the sun will be about 14; of Mercury, 93; of Venus, 5; of the Earth, 5; of the Moon, 3; of Mars, 3; of Jupiter, 1; of Saturn,; of Uranus,

99 100.

The sun's magnitude is immense, as may be judged by the fact that if he were a hollow shell, and the earth placed at the centre, there would be sufficient room for the moon to revolve, as she now does, at 240,000 miles from the earth, and there would still be some 200,000 miles beyond the moon ere the shell of the sun were reached. The planets cannot be said strictly to revolve round the sun, but the sun and the planets revolve about the centre of gravity of the system; and, owing to the preponderating bulk of the sun, this centre of gravity lies not far from his own centre.

In searching for a record of the process of creation, we naturally turn our attention to that only Book the human library contains which did not emanate from the mind of man. But the Bible was not written as an instructor in physical science, hence we only find the sacred historian dedicating a few verses to the subject of "the creation of the world." Yet we may rest assured that, although the short notice only touches the prominent points, yet every word is true; and the more science has discovered, the more has she proved to be the commentator and unfolder of the great truths contained in those few words.

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A generation since, geologists were looked upon as the opponents of revealed truth, the friends and abettors of infidels and atheists; but now we have learnt not to generalise from too few facts, but patiently to explore before pronouncing a definite judgment. The interesting questions, the development of species" and "the antiquity of man,' are to-day in the same position as the questions of "the universality of the deluge' and "the six periods of creation" at the close of the last century. But we know in these days nothing of the rancour with which the contest was then carried on. Explorers now in every part of the world collect information, and every right-minded man rests assured that in the end Scripture will not be contradicted, but confirmed.

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The chief points in the description of the creation given in Genosis will be found to be fairly explained by Laplace's nebular hypothesis, which has been extended to the explanation of the contour of the earth's surface. The first fiat of the creation was, "Let there be light." Now we are well aware that light is nothing more than the rapid vibration of an invisible existence called ether; so that our word "light" in the expression quoted must mean light-giving matter." This corresponds to the firecloud of the hypothesis. All bodies of our acquaintance are capable of existing in a state of vapour. The temperature at which this change of state takes place is so high that the vapours are luminous. Hence the first fiat of creative power called into existence all the matter of which the solar system is composed in a state of highly luminous vapour. In the expression that "the light was divided from the darkness," there seems to be an 53

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