CASSELL, PETTER, AND GALPIN,

LUDGATE HILL, LONDON, E.C.;

isuloo I

INDEX TO CONTENTS.

POPULAR EDUCATOR.

THE SUBJECT - PHYSICAL

- THE

LESSONS IN GEOLOGY.-1.

plausible of the theories yet produced to account for the can.

struction of our system, and therefore of our earth. INTRODUCTION -- DIVISIONS OF GEOLOGY

The solar system, of which we are one of the members, consists GEOLOGICAL SYSTEMS MINERALOGY AND LITHOLOGY—THE SOLAR SYSTEM, ETC. ETC.

of the sun and eight planets-four of which are very much larger

than the earth-and a number of very small planets, called asteThe derivation of the word Geology (m [ghee], the earth, and roids, which revolve in the space separating the four exterior and tóyas [log'as), a discourse, or a reasoning) indicates the main larger planets from the interior and smaller ones. The position of direction of the science. It confines its attention to a description the earth is the third from the sun. The earth is accompanied by of the solid crust of the earth, and to the elucidation of those a moon, which is not the case with any of the other interior forces and causes which have produced the changes the surface of planets, whilst the exterior planets are all attended by satellitesour planet has undergone. To aid him in his investigation, the Saturn and Uranus by eight, Jupiter by four. All these bodies geologist needs the aid of the botanist, the zoologist, the chemist, revolve round the sun in the same direction, and all move within the mineralogist, the physicist, and even of the mathematician. a narrow belt. The exterior planets are much lighter than the

Although the subject looks formidable to the general reader, interior. If the density of water be taken as 1, the density of it is not only franght with the deepest interest, but by far its the sun will be about 1}; of Mercury, 91; of Venus, 51); of greatest part may be traversed by common sense. Moreover, the Earth, 53; of the Moon, 3}; of Mars, 3}; of Jupiter, 1.4; its study commends itself to all, since it requires no expensive of Saturn, }}; of Uranus, 1.apparatas, nor yet a preparation which all other sciences The sun's magnitude is immense, as may be judged by the demand ere the student can enter on their practice. Young fact that if he were a hollow shell, and the earth placed at the and old, gifted with observation, may at once become practical centre, there would be sufficient room for the moon to revolve, geologists; and by never passing a stone-heap without an ex as she now does, at 240,000 miles from the earth, and there amination, or never leaving a quarry or gravel-pit unsearched, would still be some 200,000 miles beyond the moon ere the shell they will soon lay the foundation of a geological cabinet, and be of the sun were reached. The planets cannot be said strictly efficient labourers in the extension of geological research. to revolve round the sun, but the sun and the planets revolve

Every generation of our race has produced men of inquiring about the centre of gravity of the system; and, owing to the minds, and it is but natural that such men should turn their preponderating bulk of the sun, this centre of gravity lies not research to discover the origin of the world we inhabit, espe- far from his own centre. cially in the early times when but few channels were opened In searching for a record of the process of creation, we along which they were invited to expend the natural vigour of naturally turn our attention to that only Book the human their intellect; hence, in the earliest records of eastern nations library contains which did not emanate from the mind of man. we find theories which attempt to account for the existence of But the Bible was not written as an instructor in physical our earth these it is unnecessary to dwell upon.

science, hence we only find the sacred historian dedicating a few It is evident that the only sound mode of procedure is to collect verses to the subject of “the creation of the world." Yet we all the information which observation of the various existing may rest assured that, although the short notice only touches phenomena of nature can give; to search the crust of the earth the prominent points, yet every word is true; and the more for any facts which the rocks, their position, their character, their science has discovered, the more has she proved to be the comfossil contents, can afford; to notice the arrangement of conti- mentator and unfolder of the great truths contained in those bents and seas, the position and directions of mountain chains, few words. etc., and from these letters of the geological alphabet to spell A generation since, geologists were looked upon as the oppoout the history of our globe.

nents of revealed truth, the friends and abettors of infidels and The history of the progress of geology, like that of any other atheists; but now we have learnt not to generalise from too seience, can furnish many instances of theories built up with few facts, but patiently to explore before pronouncing a definite out any facts for foundations; but as patient research gradu- judgment. The interesting questions, “the development of elly amassed information, these erroneous suppositions were species” and “ the antiquity of man,” are to-day in the same atradoned, and geologists have, from so many warnings, be position as the questions of “the universality of the deluge" come extremely careful of hazarding opinions. The experiences and “the six periods of creation” at the close of the last century. by which we have been taught not to speculate, though interest. But we know in these days nothing of the rancour with which ing and instructive, we cannot record in these pages, as our the contest was then carried on. Explorers now in every part limited space requires us to attend to facts and the deductions of the world collect information, and every right-minded man which may be reasonably drawn from them.

rests assured that in the end Scripture will not be contradicted, The division of the subject we propose is the following : but confirmed.

1. Physical Geology—that is, the geological agencies which The chief points in the description of the creation given in have worked the various changes in the surface of our planet, Genesis will be found to be fairly explained by Laplace's

nebular both as to their present existence and as to the traces of their hypothesis, which has been extended to the explanation of the pore which the rocks reveal.

contour of the earth's surface. The first fiat of the creation was, 2. The Geological Systems.-As we pass through these, we “Let there be light.” Now we are well aware that light is shall enomerate the fossils the rocks contain, the history of the nothing more than the rapid vibration of an invisible existence animal and vegetable life of our globe, and the localities in called ether; so that our word " light” in the expression quoted which the members of these systems appear.

must mean “ light-giving matter.” This corresponds to the fire3. Mineralogy and Lithology.--In our last division we hope cloud of the hypothesis. All bodies of our acquaintance are to describe the composition of the various kinds of rocks, as capable of existing in a state of vapour. The temperature at well as the physical and chemical properties of the minerals which this change of state takes place is so high that the vapours they contain

are luminous. Hence the first fiat of creative power called into Before we enter upon the immediate province of geology, it existence all the matter of which the solar system is composed will be well to consider our position in the universe, and some in a state of highly luminous vapour. In the expression that siat of the character of our world as a globe, noticing the most ' “ the light was divided from the darkness," there seems to be ar

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