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operations, must be governed by imperative laws, and that the mineral structure of the globe arising therefrom has consequently a definite and determinable arrangement. Third, That this arrangement, as displayed in the numerous rock-formations, implies an enormous lapse of time—time to waste and wear, time to transport, and time to deposit and reconstruct—and therefore establishes an antiquity for our globe vast beyond all previous conception. Fourth, That during the long periods which these successive formations—that is, successive distributions of sea and land— imply, the earth has been peopled by different races of plants and animals—all evidently belonging to the same great scheme of life, but varying widely in their characteristics during each succeeding epoch. Fifth, That during these periods there has been an ascent, in the main, from lower to higher forms; and that the plants and animals now inhabiting the globe are, on the whole, higher and more specially organised than the plants and animals of any former period. Sixth, That these successive appearances and distributions of plants and animals are connected together in one great scheme of life by some pervading law of development which, though not yet satisfactorily discovered, is evidently bound up with the operating forces of the universe. And, lastly, The earth being still subjected to the same causes of change, and, from all we can see, to the same law of development that operated in time past, the future aspects of our planet must differ from the present physically and vitally—its present distribution of sea and land giving place to other arrangements of sea and land, and its present living races to others of a still higher and more specialised organisation.

Such is the crust we dwell upon, and the teachings which a study of its structure can convey. This rocky exterior is all we know with certainty of the composition of our planet—the foundation of all geographical diversity, the diversified habitat of plants and animals, the scene of man's own life-labours, and the storehouse of those minerals and metals upon which his civilisation and progress are so intimately dependent. The study of its structure is replete with intellectual interest of the most exalted description. The variety of its rock-formations, the minerals and metals they contain, their modes of aggregation, and the curious changes to which they have been subjected in their repeated alternations from sea to land and from land to sea, are all calculated to excite our interest and increase our admiration of the means employed by the Creator to alter, to diversify, and to sustain. And that interest and admiration are increased a hundredfold when we perceive in these formations the nature of the life that has preceded us rising through long ages from the simple to the more complex, from the simply sentient to the intellectual and reflective, and this through forms so countless and varied, and yet all belonging to the same great plan, that numerous as are the existing forms of plants and animals, they form but a tithe of those that have necessarily existed before them. No one, then, can look into the structure of this crust without receiving newer and deeper insight into the laws and ordainings of nature, and from all deeper insight of nature the human intellect arises wiser, happier, and more exalted.

But the study of the earth's crust is not less desirable from its economic advantages than from its intellectual interest. Man's civilisation and progress, and his mastery over the powers of nature, are intimately dependent upon his knowledge and application of the minerals and metals. Indeed, modern civilisation and progress have largely arisen from this knowledge of the minerals and metals; and as these hold determinate positions in the various formations of the crust, an acquaintance with that crust is indispensable to their acquisition. Gold and silver, coal and iron, gems and precious stones, are not scattered indiscriminately through the earth. Some occur more abundantly in one formation than in another; some in beds, others in veins; some exclusively in one kind of matrix, others in another; and all this knowledge as to abundance, depth of strata, direction of veins, and the like, can only be acquired by a study of the structure and arrangement of the rocky crust. Geology has thus all the interest of a wondrous Past to attract; it possesses all the value of a sterling Present to incite to its study and acquirement. To the general reader its revelations of world:history will ever form themes of intelligent attraction; to the miner, the engineer, the architect, and others whose business is to deal with the structure and products of the rocky exterior, its deductions are of direct and special importance.

Such, once more, are the economic and intellectual advantages arising from a study of the structure of the crust we dwell upon—economic advantages of which our country, in every department of its industry, is every day reaping the benefit, and intellectual promptings which have led to a newer and deeper insight into the laws and ordainings of nature. We say newer and deeper insight, for with increased knowledge of the past must extend our knowledge of the present; and the tendency of all true knowledge of God's workings in nature must ever be to make men better, wiser, and happier in all their relations to that nature of which they form so prominent a part. Everything is bound up one with another in the Divine scheme of the universe; and he who perceives this truth most fully in the physical world is surely the most likely to regard it

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in the intellectual and moral. On this ground alone, and

altogether independent of its intellectual pleasures and

economic advantages, the science of this earth-crust is

worthy of our closest cultivation—leading the mind from

the harmonies that prevail in the natural world up to the

higher harmonies that ought to pervade the human and

social.

"All are but parts of one stupendous whole,
Whose body Nature is, and God the soul;
That changed in all, and yet in all the same,
Great in the Earth, as in th' Ethereal frame."

WASTE AND EECONSTRUCTION.

THE EARTH'S CRUST SUBJECT TO INCESSANT WASTE AND RECONSTRUCTION—SLOW AND GRADUAL NATURE OF THESE CHANGES— CAUSES OR AGENCIES PRODUCTIVE OF CHANGE: 1. METEORIC OR ATMOSPHERIC—RAINS, FROSTS, AND WINDS—2. AQUEOUS—RIVERS, WAVES, TIDES, AND OCEAN-CURRENTS—3. CHEMICAL—SOLUTION AND PRECIPITATION—4. ORGANIC—PLANT AND ANIMAL GROWTHS —5. IGNEOUS—VOLCANOES, EARTHQUAKES, AND CRUST-MOTIONS— THE CRUST HELD IN EQUILIBRIUM BETWEEN WASTE AND RECONSTRUCTION—THESE ENDURING AS THE PLANETARY SYSTEM.

"Our solid earth is everywhere wasted, where exposed to the day. The summits of the mountains are necessarily degraded. The solid and weighty materials of those mountains are everywhere urged through the valleys by the force of running water. The soil, which is produced in the destruction of the solid earth, is gradually travelled by the moving water, but is constantly supplying vegetation with its necessary aid. This travelled soil is at last deposited upon the coast, where it forms most fertile countries. But the billows of the ocean agitate the loose materials upon the shore, and wear away the coast, with the endless repetitions of this act of power, or this imparted force. Thus the continent of our earth, sapped to its foundation, is carried away into the deep and sunk again at the bottom of the sea, whence it had originated, and from which, sooner or later, it will again make its appearance. We are thus led to see a circulation in the matter of this globe, and a system of beautiful economy in the works of nature." Such are the words of Dr Hutton in his celebrated 'Theory of the

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