In mathematics, the branch which most nearly approaches pure reason, least advance has been made. There was least room for it. Newton, when, at quite a mature period of his career, Euclid was first brought to his attention, laid the book down after a cursory glance with the remark that it was only fit for children, its propositions being self-evident. Yet to those truisms Newton added very little. His work lay in their development and application. Laplace and Biot belong to our own day; but their task, too, consisted in the employment of old rules. The most effective tools of the mathematician are framed from the Arab algebra and Napier's logarithms. The science itself without application is, like logic, a soul without a body. The field most fruitful under its application is that of astronomy. Here, progress has been great. A measuring-rod has been provided for the depths of space by the ascertainment of the sun's distance within a three-hundredth part of that body's diameter. The existence of a cosmic ether, a resisting medium, has been established, and its retarding influence calculated. Many of the nebulae have been reduced, and others proved to be in a gaseous condition, like comets. The latter bodies have been chained down to regular orbits, followed far beyond those of the old planets, and brought into genealogical relations with these through the links of bolides and asteroids. The family circle of planets proper has been immensely increased, a new visitant to the central fire appearing every few years or even months. Newton connected the most distant points of the universe by the one principle of gravitation: the spectroscope unites them by identity of structure and composition. Improved instruments have detected the parallax of a number of the fixed stars, and traced motion in both solar and stellar systems as units. Coming homeward from the distant heavens, the advances of astronomy diminish as we near what may be called the old planets and our pale companion the moon. The existence of a lunar atmosphere and the habitability of Mars are still debated; with, we believe, the odds against both. But the star-gazers make their craft useful in a novel way when it reaches the earth. Upon the precession of the equinoxes they erect a fabric of retrograde chronology, and set a clock to geologic time. Here Sir Isaac is brought to grief. His excursions beyond the Deluge are proved blind guides. He misleads us among the ages as sadly as Archbishop Usher. The profoundest of laymen and the most learned of clerics are equally at sea in locating creation. That successive phases of animate existence were rising and fading with the oscillations of the earth's inclination to its orbit never occurred to him to whom "all was light." To probe the stars was to him a simpler process than to anatomize the globe upon which he stood.