Even in the minds of those who cultivate a particular branch of knowledge, there is often an internal secret despair of finding the truth, which so far paralyzes their efforts as to prevent them from seeking it with that deep earnestness, without which it is seldom found. The history of optics furnishes a most impressive illustration of the justness of this remark. Previous to the time of Newton, no one seemed to entertain a real hope that this branch of knowledge would ever assume the form and clearness of scientific truth. The laws and properties of so ethereal a substance as light, appeared to elude the grasp of the human intellect; and hence, no one evinced the boldness to grapple directly with them. The whole region of optics was involved in mists, and those who gave their attention to this department of knowledge, abandoned themselves, for the most part, to vague generalities and loose conjectures. In the conflict of manifold opinions, and the great variety of hypotheses which seemed to promise nothing but endless disputes, the highest idea of the science of optics that prevailed, was that of something in relation to light which might be plausibly advanced and confidently maintained. It was reserved for Newton to produce a revolution in the mode of treating this branch of knowledge, as well as that of physical astronomy. Not despairing of the truth, he sternly put away “innumerable fancies flitting on all sides around him,” and by searching observation and experiment, brought his mind directly into contact with things themselves, and held it steadily to them, until the clear light of truth dawned. The consequence was, that the dreams of philosophy, falsely so called, gave place to the clear realities of nature. It was to the unconquerable hope, no less than to the profound humility of Newton, that the world is indebted for his most splendid discoveries, as well as for that perfect model of the true spirit of philosophy, which combined the infinite caution of a Butler with the unbounded boldness of a Leibnitz. The lowliest humility, free from the least shadow of despair, united with the loftiest hope, without the least mixture of presumption, both proceeding from an invincible love of truth, are the elements which constituted the secret of that patient and all-enduring thought which conducted the mind of Newton from the obscurities and dreams enveloping the world below into the bright and shining region of eternal truths above. In our humble opinion, Newton has done more for the great cause of knowledge, by the mighty impulse of hope he has given to the powers of the human mind, than by all the sublime discoveries he has made. For, as Maclaurin says: “The variety of opinions and perpetual disputes among philosophers has induced not a few of late, as well as in former times, to think that it was vain labour to endeavour to acquire certainty in natural knowledge, and to ascribe this to some