LIST OF ILLUSTRATIONS.
BY S. & G. NICHOLLS.
| PAGE | |
|---|---|
| Basaltic Columns, Regia, Mexico | [Frontispiece.] |
| Section of the Earth’s Crust | [16] |
| Ditto | [21] |
| London Basin | [25] |
| Section of ditto | [25] |
| Artesian Well | [27] |
| Mining District | [41] |
| Section of a Mine | [43] |
| Trilobite | [56] |
| Ditto | [57] |
| Eyes of ditto | [58] |
| Crystallization on Cornish Slate | [60] |
| Bellerophon | [61] |
| Silurian Remains | [61] |
| Ditto | [62] |
| Coralline | [62] |
| Land’s End | [66] |
| Fish Scales | [74] |
| Fish Tails | [75] |
| Cephalaspis | [76] |
| Coccosteus | [77] |
| Pterichthys | [78] |
| Osteolepis | [79] |
| Extinct and existing Ferns | [87] |
| Flora of the Carboniferous System | [95] |
| Asterophyllite and Sphenopteris | [97] |
| Pecopteris, Odontopteris, and Neuropteris | [98] |
| Calamites | [100] |
| Stigmaria Ficoides | [101] |
| Miner at Work, and Lamp | [105] |
| Casts of Rain drops | [111] |
| Footprints of Bird | [113] |
| Ditto | [114] |
| Footprints of Labyrinthodon | [116] |
| Ammonites | [130] |
| Ditto and Nautilus | [131] |
| Ditto | [132] |
| Ichthyosaurus | [137] |
| Plesiosaurus | [140] |
| Dirt-Bed, Portland | [150] |
| Oolite Coral | [151] |
| Ditto | [152] |
| Pear Encrinites | [164] |
| Ditto | [165] |
| Ditto, with Coral | [166] |
| Ammonites Jason | [166] |
| Oolite Shells | [169] |
| Discovering the Pterodactyle | [170] |
| The Philosopher and Ditto | [171] |
| Pterodactyle Skeleton | [173] |
| Ditto, restored | [174] |
| Fauna of the Oolitic Period | [195] |
| Royston Heath | [206] |
| Fossil Teeth (Greensand) | [209] |
| Fossils from the Gault (Folkstone) | [210] |
| Ditto | [211] |
| Fossils from the Chalk | [212] |
| Fossil Fish | [214] |
| Ditto | [215] |
| Waltonian and Mantellian Fishermen | [223] |
| Fossils from the London Clay | [238] |
| Wood perforated by the Teredina | [241] |
| Septaria | [242] |
| Fossils from Red Crag | [245] |
| Megatherium | [248] |
| Mastodon | [250] |
| Fossil Man | [251] |
| Cliff, Guadaloupe | [252] |
| The Geologist’s Dream | [254] |
| The Reconciliation | [288] |
GEOLOGY.
CHAPTER I.
INTRODUCTORY.
“In the beginning God created the heaven and the earth.”
Moses.
Geology is the history of the crust of this planet. This history we compile, not from old records or moth-eaten state papers, not from antiquarian research or the study of ancient coins, but from actual and painstaking examination of the materials composing this crust. How suitable is this word crust, will be seen at once, when it is considered that its thickness in all probability does not exceed eighty miles, a mere fraction of the distance to the earth’s centre. Of this eighty miles we know pretty accurately the character and arrangement of some seven or eight miles; not that we have ever penetrated so far beneath the surface in a straight line, the deepest mines not exceeding 1800 or 1900 feet; but, by putting together the thicknesses of the various strata, with which we are well acquainted, we reach this conclusion without much hesitation. Professor Whewell has well observed, that “an earth greater or smaller, denser or rarer, than the one on which we live, would require a change in the structure and strength of all the little flowers that hang their heads under our hedges. There is something curious in thus considering the whole mass from pole to pole and from circumference to centre, as employed in keeping a snowdrop in the position most suited to its vegetable health.”[[1]] When we come to examine this crust, several appearances of a striking character reward our toil. At first, and before we proceed in our investigations more minutely, we find that there are only two varieties of rocks in all the vast arrangements spread out before us. Some rocks we find to be unstratified, and others we find to be stratified: from the absence of all fossils in the former of these, and from their crystalline character, we conclude that these were formed by the action of fire, and therefore we call them Igneous or Plutonic rocks. From the sedimentary character and from the numerous fossils of the stratified rocks, we conclude these to have been formed by the action of water, and we therefore call these Aqueous or Neptunian rocks. Following out these investigations, we meet with other facts equally interesting: we find that the Plutonic or unstratified rocks lie generally at the base of all the others, and that where they come up to the surface and crop out from other rocks, or rise in towering mountain heights above them, this has been the result of igneous action from beneath, and that this elevation has disturbed the surrounding strata from the horizontal position in which we imagine them to have been first arranged. The extent of the Plutonic rocks is immense; in Europe, the Scandinavian mountains, the Alps, the Pyrenees, and the Carpathians; in Asia, the Himalayan, the Caucasian, and the Altai mountains; in Africa, the Atlas mountains and the Cape of Good Hope; in America, nearly the whole of the two continents, and in Australia, its southern part;—all these wide regions of the globe are composed of those igneous or Plutonic rocks to which we give the names of granite, basalt, porphyry, trap, &c. &c. Finding the surrounding strata disturbed by depression, or upheaval in consequence of the giant claims of these older rocks that appear to have risen out of the centre of the earth in a red-hot or semifluid condition, and then suddenly to have cooled down, we begin to examine this upper and sedimentary strata, and here the most delightful and romantic results are obtained. We find no two courses or formations in these sedimentary rocks alike. Rising up from the granite, we meet in the clay strata corals and trilobites, the first fossil forms of ancient life with which we are acquainted: we rise higher still, for our imaginary start is from the bottom of the earth’s crust, and we meet in other rocks fossil fishes of an extraordinary shape, and once, doubtless, possessed of extraordinary functions; higher yet, and touching the coal measures, we come to vast forests of palms and ferns, that by chemical changes and mechanical pressure have been converted into our mineral coal, the vast fields of which constitute the real diamond mines of Great Britain; higher yet, exploring the Lias and Oolitic groups, the huge remains of ancient saurians (animals of the lizard species) fill us with awe and wonder, and make us rejoice that they had no successors in the next strata; higher yet, and we reach the last period of the earth’s history, previous to the introduction of man, and enormous “four-footed beasts,” the mastodon, the megatherium and others, astonish us by their gigantic proportions, and evidently herbivorous habits; and last of all we rise to the surface and breathe freely in company with our fellow man, made in the image of God, to inhabit this world as his palace, and to interpret its mysteries as its priest.
We may probably put these general results into a more popular form,—for we reserve the details to a seriatim examination of each formation,—by the following quotation from a modern and extensively useful writer: “We distinguish four ages of nature, corresponding to the great geological divisions, namely—
“1. The primary or palæozoic[[2]] age, comprising the Lower Silurian, the Upper Silurian, and the Devonian. During this age there were no air-breathing animals. The fishes were the masters of creation. We may therefore call it the Reign of Fishes.