(311.) It is only since a comparatively recent date, however, that any great attention has been bestowed on the smaller stars, among which there can be no doubt of the most interesting and instructive phenomena being sooner or later brought to light. The minute examination of them with powerful telescopes, and with delicate instruments for the determination of their places, has, indeed, already produced immense catalogues and masses of observations, in which thousands of stars invisible to the naked eye are registered; and has led to the discovery of innumerable important and curious facts, and disclosed the existence of whole classes of celestial objects, of a nature so wonderful as to give room for unbounded speculation on the extent and construction of the universe. (312.) Among these, perhaps the most remarkable are the revolving double stars, or stars which, to the naked eye or to inferior telescopes, appear single; but, if examined with high magnifying powers, are found to consist of two individuals placed almost close together, and which, when carefully watched, are (many of them) found to revolve in regular elliptic orbits about each other; and so far as we have yet been able to ascertain, to obey the same laws which regulate the planetary movements. There is nothing calculated to give a grander idea of the scale on which the sidereal heavens are constructed than these beautiful systems. When we see such magnificent bodies united in pairs, undoubtedly by the same bond of mutual gravitation which holds together our own system, and sweeping over their enormous orbits, in periods comprehending many centuries, we admit at once that they must be accomplishing ends in creation which will remain for ever unknown to man; and that we have here attained a point in science where the human intellect is compelled to acknowledge its weakness, and to feel that no conception the wildest imagination can form will bear the least comparison with the intrinsic greatness of the subject. _Geology._