The remainder of this work will be devoted to an investigation of the changes now going on in the crust of the earth and its inhabitants. The importance which the student will attach to such researches will mainly depend in the degree of confidence which he feels in the principles above expounded. If he firmly believes in the resemblance or identity of the ancient and present system of terrestrial changes, he will regard every fact collected respecting the causes in diurnal action as affording him a key to the interpretation of some mystery in the past. Events which have occurred at the most distant periods in the animate and inanimate world, will be acknowledged to throw light on each other, and the deficiency of our information respecting some of the most obscure parts of the present creation will be removed. For as, by studying the external configuration of the existing land and its inhabitants, we may restore in imagination the appearance of the ancient continents which have passed away, so may we obtain from the deposits of ancient seas and lakes an insight into the nature of the subaqueous processes now in operation, and of many forms of organic life, which, though now existing, are veiled from sight. Rocks, also, produced by subterranean fire in former ages, at great depths in the bowels of the earth, present us, when upraised by gradual movements, and exposed to the light of heaven, with an image of those changes which the deep-seated volcano may now occasion in the nether regions. Thus, although we are mere sojourners on the surface of the planet, chained to a mere point in space, enduring but for a moment of time, the human mind is not only enabled to number worlds beyond the unassisted ken of mortal eye, but to trace the events of indefinite ages before the creation of our race, and is not even withheld from penetrating into the dark secrets of the ocean, or the interior of the solid globe; free, like the spirit which the poet described as animating the universe, ----ire per omnes Terrasque, tractusque maris, coelumque profundum. BOOK II. CHANGES IN THE INORGANIC WORLD. AQUEOUS CAUSES. CHAPTER XIV. Division of the subject into changes of the organic and inorganic world--Inorganic causes of change divided into aqueous and igneous--Aqueous causes first considered--Fall of rain--Recent rain-prints in mud--Destroying and transporting power of running water--Newly formed valleys in Georgia--Sinuosities of rivers--Two streams when united do not occupy a bed of double surface--Inundations in Scotland--Floods caused by landslips in the White Mountains--Bursting of a lake in Switzerland--Devastations caused by the Anio at Tivoli--Excavations in the lavas of Etna by Sicilian rivers--Gorge of the Simeto--Gradual recession of the cataract of Niagara.