When we examine the internal structure of a plant or animal, a wonderful subtility of mechanism is displayed. Man, in his mechanical operations, is confined to the surface of bodies. But the operations of nature are exerted through the whole substance, so as to reach even the elementary parts. Thus the body of an animal, and of a plant, are composed of certain great vessels; these of smaller; and these again of still smaller, without end so far we can discover. This power of diffusing mechanism through the most intimate parts, is peculiar to nature; and distinguishes her operations, most remarkably, from every work of art. Such texture, continued from the grosser parts to the most minute, preserves all along the strictest regularity. The fibres of plants are a bundle of cylindric canals, lying in the same direction, and parallel or nearly parallel to each other. In some instances, a most accurate arrangement of parts is discovered, as in onions, formed of concentric coats one within another to the very centre. An animal body is still more admirable, in the disposition of its internal parts, and in their order and symmetry. There is not a bone, a muscle, a blood-vessel, a nerve, that hath not one corresponding to it on the opposite side of the animal; and the same order is carried through the most minute parts. The lungs are composed of two parts, which are disposed upon the sides of the thorax; and the kidneys, in a lower situation, have a position not less orderly. As to the parts that are single, the heart is advantageously situated nigh the middle. The liver, stomach, and spleen, are disposed in the upper region of the abdomen, about the same height: the bladder is placed in the middle of the body; as well as the intestinal canal, which fills the whole cavity by its convolutions. The mechanical power of nature, not confined to small bodies, reacheth equally those of the greatest size; witness the bodies that compose the solar system, which, however large, are weighed, measured, and subjected to certain laws, with the utmost accuracy. Their places around the sun, with their distances, are determined by a precise rule, corresponding to their quantities of matter. The superior dignity of the central body, in respect of its bulk and lucid appearance, is suited to the place it occupies. The globular figure of these bodies, is not only in itself beautiful, but is above all others fitted for regular motion. Each planet revolves about its own axis in a given time; and each moves round the sun, in an orbit nearly circular, and in a time proportioned to its distance. Their velocities, directed by an established law, are perpetually changing by regular accelerations and retardations. In fine, the great variety of regular appearances, joined with the beauty of the system itself, cannot fail to produce the highest delight in every person who can taste design, power, or beauty.