principal difficulties that have arisen, are owing to the improper manner in which the subjects connected with natural history have often been treated. Natural philosophy regards what was the condition of natural bodies: but many persons exert the whole force of their genius to discover what they _might have been_. And as there is no department of natural philosophy into which this erroneous method of procedure has made greater inroads than geology, nor any science that has suffered so severely in such conflicts, it may not be amiss to appropriate half an hour to the inquiry whence this error has arisen; and, if possible, point out the best method of avoiding its dangerous tendency. The word geology is derived from two Greek words, signifying "the earth" and "reason;" and it is that science which teaches the structure of the crust of the earth, and ascertains its mineralogical materials, and the order in which they are disposed, and their relations to each other. Geognosy is used by the French as synonymous to geology, but in English is generally understood to be synonymous to cosmogony; which is an inquiry, or rather a speculation, as to the original formation or creation of the world; hence geognosy has sometimes been called "speculative geology." In pursuing the examinations to which geology leads, we reason from facts, as is done in other branches of natural science. The strata of the crust of the earth, owing to the disturbed manner in which we now find them, are in a great measure open to our examination; their composition, formation, deposition, eruption, depression, succession, and mineralogical contents, are all objects of sensation. The objects of geognosy (in the English sense of the word) are, on the other hand, for the most part, ideal, visionary and delusive. We are sensible that this earth exists and that it is material, and therefore we know that it must have been created. We know that it was not created by man, who hath not the power to add to it one single atom, nor diminish it by a single grain--so that it is manifest that it was created by a superior and omnipotent power; but by what process it was done is a mystery, and the more we seek to discover it the more we expose our ignorance. The geologist, like the mathematician, deals with the understanding; his advance is wary, admitting no conclusion until his premises are fully established. The professor of geognosy, on the contrary, addresses himself entirely to the imagination, and he delights in hypothesis and suppositions. The progress of the geologist is necessarily slow; he is like the patient miner, making his laborious but determined way into the solid rock: but the professor of geognosy will make a world or even a universe in an hour, for he deals in fancy and works in visionary speculations. The geologist delves into the bowels of the earth in search of useful metals, earths and combustible matters, which nature has kindly placed