The surface of the globe exposes to the eye of the Geognost abundant evidence of a variety of changes which appear to have succeeded one another during an incalculable lapse of time. These changes are chiefly, I. Variations of level between different constituent parts of the solid surface of the globe. II. The destruction of former rocks, and their reproduction under another form. III. The production of rocks _de novo_ upon the earth's surface. Geologists have usually had recourse for the explanation of these changes to the supposition of sundry violent and extraordinary catastrophes, cataclysms, or general revolutions having occurred in the physical state of the earth's surface. As the idea imparted by the term Cataclysm, Catastrophe, or Revolution, is extremely vague, and may comprehend any thing you choose to imagine, it answers for the time very well as an explanation; that is, it stops further inquiry. But it has also the disadvantage of effectually stopping the advance of science, by involving it in obscurity and confusion. If, however, in lieu of forming guesses as to what may have been the possible causes and nature of these changes, we pursue that, which I conceive the only legitimate path of geological inquiry, and begin by examining the laws of nature which are actually in force, we cannot but perceive that numerous physical phenomena are going on at this moment on the surface of the globe, by which various changes are produced in its constitution and external characters; changes extremely analogous to those of earlier date, whose nature is the main object of geological inquiry. These processes are principally, I. The Atmospheric phenomena. II. The laws of the circulation and residence of Water on the exterior of the globe. III. The action of Volcanos and Earthquakes. The changes effected before our eyes, by the operation of these causes, in the constitution of the crust of the earth are chiefly-- I. The Destruction of Rocks. II. The Reproduction of others. III. Changes of Level. IV. The Production of New Rocks from the interior of the globe upon its surface.