By “conducting the eye to the confines of the visible form,” the Microscope proves an effective auxiliary in defining the geometric properties of bodies. Its influence as an instrument of research upon the structure of bodies has been compared to that of the galvanic battery, in the hands of Davy, upon Chemistry. It detects the smallest structural difference, heretofore inappreciable, and, as an ally of Chemistry, enables us to discover the very small changes of form and colour effected by test-fluids upon solids; and dissects for us, so to speak, the most multiplex compounds. It opens out to the mind an extended and vast tract, opulent in wonders, rich in beauties, and boundless in extent. The Microscope not only assists studies, and develops objects of profound interest, but also opens up innumerable sources of entertainment and amusement, in the ordinary conventional acceptation of these terms; disclosing to us peculiarities and attractions in abundance; impressing us with the wonderful and beautifully skilful adaptation of all parts of creation, and filling our minds with additional reverence and admiration for the beneficent and Almighty Creator. The Author will conclude these prefatory observations with a few words in explanation of his arrangements, by way of dealing with the instrument and development of his subject. He has sought, in the volume that he now lays before the public, to point out and elucidate at once in a practical manner and in a popular style, the vast fund of utility and amusement which the Microscope affords, and has endeavoured to touch upon most of the interesting subjects for microscopic observation as fully as the restrictions of a limited space, and the nature of the succinct summary, would permit. To have dwelt upon each in complete detail would have necessitated the issue of many expensive volumes--and this would have entirely frustrated the aim which the writer had in view; he has, therefore, contented himself with the humble, but, he trusts, not useless, task of setting up a finger-post, so to say, to direct the inquirer into the wider road. In the section of the work devoted to the minuter portion of creation, he has ventured to dwell somewhat longer, in the belief that that department is more especially the province of the microscopist. He has arranged his topics under special headings, and in separate chapters, for the sake of perspicuity and precision; and has brought the ever-welcome aid of illustration to convey his explanatory remarks more vividly to the minds of his readers.