The description of the Lucretian atom is wonderfully applicable to the chemical atom, the existence of which, already quite a complex little world, is highly probable. We are not wholly without hope that the real weight of each atom may some day be known, and their number in each material ; that the form and motion of the parts of each atom, and the distance they are separated, may be calculated ; that the motions by which they produce light, heat, and electricity may be illustrated by exact geometrical diagrams; then the motion of the spheres will be neglected for a while, in admiration of the maze in which the tiny atoms turn. Yet when we have found a mechanical theory by which the phenomena of inorganic matter can be mathematically deduced from the motion of materials endowed with a few simple properties, we must not forget that Democritus, Leucippus, and Epicurus began the work ; and we may even now recognize their merit, and acknowledge Lucretius not only as a great poet, but as the clear expositor of a very remarkable theory of the constitution of matter. - North British Review, 1868.