If we employ the microscope, far greater wonders of divisibility than these appear, even in the complex organization of animal life. Ehrenberg has shown that tripoli, a mineral much used in the arts, is entirely composed of the siliceous shells of the microscopic animalcula, known as infusiorials, and that a single cubic inch of it contains at least _forty-one thousand millions_ of these shells!--about fifty times as many individuals as there are of human beings on the globe. Yet each of these minute animals lived and fed; had digestive and circulative systems, with blood possessing globules as large, probably, in proportion, as those of ours, besides nerves of sensation and inclination, with brains belonging to them, together with muscles and every other mechanical apparatus for the extremely active locomotion and propagation which they so interestingly exhibit. And every new improvement in the microscope reveals new races of animals, apparently created for their own enjoyment, and of which millions heaped on millions, would be utterly invisible to the unaided eye.--These facts prove that things are great and small only by comparison with each other, and not in relation to infinity, with which no comparison can be instituted. And they prove, moreover, that vain, boastful, and bigoted man, is not the sole object of creation, nor of the profound benevolence, contrivance and design, with which it is universally replete.--_Art's Echo._ * * * * * IRON--ITS NATURAL AND ARTIFICIAL COMBINATIONS WITH CARBON. The question is often asked, what constitutes the difference between wrought iron, cast iron and steel? Cast Iron, when viewed under favorable circumstances, by the help of a microscope will be found to be a mechanical aggregation of molecules of _iron and carbon_; and the relative position of these particles may be illustrated by a pile of cannon balls as usually arranged in navy yards, each alternate ball being iron and carbon (charcoal).