« ПредыдущаяПродолжить »
ages would now be insufficient. In contemplating the production of rivers, he regards them as having cut their own way to the sea, and in their course gradually wearing down the mountainous lands, filling up vallies, and choaking their exits into the ocean by finely divided materials : thus every thing is slowly returning to its former state; all mountains shall be levelled, every valley raised up, excavations filled up, and the ocean will again cover the earth. I shall not enter into the various confutations which these speculative notions have met with, nor dwell upon many modern theories to which they have given rise ; for though the authors of these theories have sometimes clothed their fictions in new dresses, we have no sooner removed the mask, than Burnet or Buffon is instantly recognized.
“ The prevailing theories of the present day are the inventions of Professor Werner, of Freyburgh, and Dr. James Hutton, of Edinburgh ; each of these has been ably supported and elucidated by the proofs, illustrations, and comparative views of acute and eloquent controversialists, and two sects of geologists have been formed under the appellation of Wernerians and Huttonians.
“ The first principle which the Wernerian theory assumes, is, that our globe was once covered with a sort of chaotic compost, holding, either in solution or suspension, the various rocks and strata which now present themselves to us as its exterior crust. From some unexplained cause, this fluid began first to deposit those bodies which it held in chemical solution, and thus a variety of crystallized rocks were formed. In these we find no vegetable or animal remains,
. nor even any rounded pebbles ; but in the strata, which lie upon the crystalline, or first deposits, shells and fragments occasionally occur : these therefore have been termed transition strata ; and it is imagined, that the peopling of the world commenced about this period. The waters upon the earth began now more rapidly to subside, and finely divided particles, chiefly resulting from disintegration of the first formations, were its chief contents ;—these were deposited upon the transition rocks, chiefly in horizontal layers. They abound in organic remains, and are termed by Werner, Floetz, or secondary rocks.
“ It is now conceived, that the exposure of the primitive transition, and secondary rocks to the agencies of the wind and weather, and to the turbulent state of the remaining ocean, produced inequalities of surface, and that the water retreated into low lands and vallies, where a further deposition took place, constituting clay, grável, and other alluviat formations.
“ There are also certain substances which instead of being found in regularly alternating layers over the earth, are met with in patches; as Rock-salt, coal, basalt, and some other bodies, which Werner hath called subordinate formations. Lastly, subterraneous fires have sometimes given birth to peculiar and very limited products; and these are called volcanic rocks. Such is Werner's account of the production of rocks, which he arranges under the terms primary transition, secondary, alluvial, subordinate,and volcanic formations.
“ Hutton, looking upon the face of nature, gives a very different account of the present order of things, and observes every thing in a state of decay; but as she has obviously provided for the regeneration of animal and vegetable tribes, The philosopher descries in this apparent destruction of the surface of the earth, the real source of its renovation.
“ The stupendous mountains exposed to the action of the varying temperature of the atmosphere, and the waters of the clouds, are, by slow degrees, suffering constant diminution; their fragments are dislodged, masses are rolled into the valley, or carried by the rushing torrent into rivers ; whence they are transported to the sea. The lower and softer rocks are undergoing similar but more rapid destruction. The result of all this must be, the accumulation of new matter in the ocean, which will be deposited in horizontal layers.
“ Hutton perceives the transition rocks of Werner, though not strictly crystalline, made up apparently of finely divided matter, more or less indurated; sometimes very hard in tex.' ture, and of a vitreous fracture ; that this hardening is most perceptible when in contact with the primitive or inferior rock, which often pervades the transition rocks in veins, or appears to have broken up or luxated the superincumbent
• The transition or secondary rocks of Werner, were, according to Hutton, deposited at the bottom of the ocean, in consequence of operations similar to those which are now active, and the primary rocks were formed beneath them by the operation of subterraneous fires ; their crystalline texture, their hardness, their shape and fracture, and the alterations they have produced upon their neighbours, are the
proofs of the correctness of these views. It is by the action of fire then, that rocks have been elevated, that strata have been hardened, and that those changes have resulted, which, an examination of the earth's surface, unfolds. The production of soils and of alluvial lands, is considered as dependant upon causes the same as those referred to in the other theory. To conclude this introduction, you will observe, that Hutton refers to fire as well as water, for the production of our present rocks; the former, consolidating, hardening, and elevating; the latter, collecting and depositing the strata.
“ These, my dear Edward, are the principal systems of geology that have excited the attention and study of the learned of late years.
It remains now for us to take a general survey of the earth as to its superficial contents and po: pulation.
“ The surface of the earth then contains about 198,956,786 square miles, more than two-thirds of which are covered. with water, as may be proved by taking a map of the world, and cutting out all that part of it, which is assigned to the continents and islands, from what is allotted to the oceans, seas, gulfs, bays, and lakes. Then, putting the land in one scale, and the water in another, we shall find the latter one-third heavier than the former,
“ The seas and unknown parts are said to contain: 159,966,217 square miles, and the inhabited parts 38,990,569, of which Europe contains
4,456,065 square miles. Asia
“ Now as respects the human beings who inhabit the earth, the following table has been given as an estimate of their numbers.. Asia contains
500,000,000 of souls. Europe
" And now, Edward, can you tell me how many persons there will be to every square mile of ground in each of the quarters of the globe ?”
Admitting your calculations to be accurate, Sir," replied Edward, "the population to every square mile will be, to Europe 34 nearly, to Asia 46, to Africa 3, and in America there are only 3 inhabitants to every 2 square miles."
DR. WALKER and his pupil pursued the route to Oxford, without any interruption: it was evening when they entered this city of palaces, and the next day Dr. Walker purposed continuing their journey. "le to attempt a description of this beautiful city and its colleges," continued he, " would be to attempt an Herculean task; a volume, indeed, would scarcely suffice to detail the beauties and wonders it contains. As to the foundations of the different colleges, by whom, and when, any geographical book will give you that. Months might be profitably occupied in inspecting the different libraries, churches, and colleges; and, as I hope, when we return from our tour, we shall spend many pleasant days together within the walls of Christ-church, I do not chụse you should take a superficial glance of what is deserving a very large portion of your time and attention. I myself was brought up at Cambridge, and I confess I feel anxious you should also visit that University; though you must prosecute your studies at Oxford, because I am well acquainted. with the partiality your father had for Oxford. We used, in days of yore, to have many amicable disputes, together as to the superiority of the two colleges. I am well aware that Cambridge must yield to Oxford, as far as outward splendour goes, but, being a Cantab, I am bound to support the reputation of that University, to which I am so much indebted, against all who shall dare to dispute it,
“ Thus you see Edward, how we are beset with preju. dices.”
Early on the following morning our travellers quitted Oxford for Woodstock, wlich is celebrated for having been the residence of many of our English monarchs, and for being the spot where Henry II. concealed Rosamond, daughter of Lord Clifford, his favourite mistress. There is still pointed out a quadrangular receptacle of pure water, flowing
from a little spring under the hill, which is called her well. There are now no remains of the labyrinth, though so late as the middle of the last century part of that, as well as of the old palace, were then in existence. In the year 1705, the manor was settled on John, Duke of Marlborough, by act of Par. liament, and the present superb house, called Blenheim, was erected for his use. This estate is held by the deposit of a small square pale-blue flag in Windsor castle, which must be sent every year, on a particular day, before twelve o'clock.. On this slender offering depends the estate. An omission of this flag would forfeit the whole magnificent tenure. Woodstock has a very fine manufacture of gloves, and formerly it had one of steel watch chains, which are now totally out of date. Upon arriving at Bicestre, ourtravellers were not a little disappointed at hearing there were no horses at the inn; but the landlord assured them he expected a pair in every moment. When the poor animals arrived, they looked knocked up, and neither the doctor nor his pupil could bear the idea that they should go out again. They accordingly ordered beds, and proposed strolling about the environs of the town in the evening. It, however, proved wet, and they were obliged to content themselves at home, when the following conversation took place.
DR. WALKER.--"Come, Edward, ring for the landlord, perhaps he can lend us some old Magazines, which would while away an hour pleasantly, for it is not worth our pains to unpack our poetic library to night.”
The landlord said, he would do his best, and soon made his appearance, bringing in a large parcel of old magazines, pamphlets, newspapers, and so forth. Dr. Walker.“ We shall not lack amusement I perceive, and we are much indebted to
landlord.' LANDLORD.- :-“ Not at all, Sir. I am very glad I have been able to accommodate you. I am sorry you could not take your walk, for I should have been proud of pointing out to