The greatest natural operations are produced by the most simple and apparently inadequate agents: for as the illustrious Galileo emphatically remarked, "_La nature fait beaucoup avec peu, et ses opérations sont toutes également merveilleuses._" The profound thinker Hobbes, in the same spirit observes, "The majesty of God appeareth no less in small things than in great, and as it exceedeth human sense in the immensity of the universe, so also doth it in the smallness of the parts thereof." This sublime truth is strongly impressed on the mind of the geological inquirer, who perceives that whole countries and mountain ranges of great elevation and extent, are wholly composed of the aggregated remains of beings of such infinite minuteness that but for the powerful optical instruments of modern times, their presence would never have been suspected. A few years only have elapsed since the sagacious Ehrenberg first drew attention to this subject, and pointed out the proper method of investigation;[AV] and so rapid has been the progress of discovery in this department of science, that _infusorial deposits_, as these beds of fossil animalcules are designated, have been detected in every quarter of the globe. A fact equally unexpected and remarkable has also been established, namely, that at the present moment similar minute living agents are largely contributing to the increase of the solid materials of the crust of our planet. [AV] See '_Medals of Creation_,' p. 244, for instructions for the microscopical examination of earths, chalk, &c. [Sidenote: RICHMOND EARTH.] The infusorial earth of Virginia, alluded to in the text, is a yellowish siliceous clay, forming a deposit from twelve to fifteen feet in thickness, upon which the towns of Richmond and Petersburgh are built. The surface of the country over which it extends is characterized by a scanty vegetation, owing to the siliceous nature of the soil dependent on the minute organisms of which it almost entirely consists. When a few grains of this earth are properly prepared for microscopic examination, immense numbers of the shields or cases of animalcules are visible under a magnifying power of 300 diameters; in fact, the merest stain left by the evaporation of water in which some of the marl has been mixed, teems with these fossil remains.[AW] [AW] Specimens of Infusorial earths, prepared for the microscope, may be obtained of Mr. Topping, 4, New Winchester Street, Pentonville Hill, New Road, London.