Page:Popular Science Monthly Volume 5.djvu/401



NIMAL instincts, when properly considered, are often found to be connected with physical laws. Even in the case of man, his gratifications and dislikes frequently originate in the imperceptible action of external circumstances, and those feelings, and the impulses to which they give rise, are, in the scheme of Nature, strangely bound up with other things, with which, at first sight, they seem to have no kind of connection.

Thus, with what pleasure the whole animal world rejoices at the coming of spring! There is a heart-felt delight, not limited to the higher races, but common to all. With the returning temperature, birds, and beasts, and insects, prepare for the duties of a new year, and every thing seems full of animation and life. Even the illiterate man cannot look unmoved on the green tint stealing over the fields. Perhaps his sentiments may in some measure be connected with a perception that there is a promise for the gratification of his baser animal appetites, and that this prosperous beginning will end in the production of corn and wine for his use. But, behind these, which are the more obvious, there are other causes for rejoicing—causes which can only be fully appreciated by the intelligent, and which have been made plain only by the advances of the highest branches of human knowledge.

How often is our admiration aroused by the work of mechanical artists!—the steamship, which day after day has continued its unceasing and successful struggles with the waves, or the chronometer, which, once wound up, keeps on for months together its regulated motion. Yet how far are all these contrivances outdone in the mechanism of every living man! Of his double nervous system, one part, the intellectual, observes its mysterious periodicities, its time of activity and time