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_. “2. The _secondary_ age, comprising the carboniferous formation, the trias, the oolitic, and the cretaceous formations. This is the epoch in which air-breathing animals first appear. The reptiles predominate over the other classes, and we may therefore call it the _Reign of Reptiles_. “3. The _tertiary_ age, comprising the tertiary formations. During this age, terrestrial mammals of great size abound. This is the _Reign of Mammals_.