varieties in nature enables us, within certain limits, to conceive other varieties analogous to them. We can conceive the sun or moon falling; for although we never saw them fall, nor ever perhaps, imagined them falling, we have seen so many other things fall, that we have innumerable familiar analogies to assist the conception; which after all, we should probably have some difficulty in framing, were we not well accustomed to see the sun and moon move, (or appear to move,) so that we are only called upon to conceive a slight change in the direction of motion, a circumstance familiar to our experience. But when experience affords no model on which to shape the new conception, how is it possible for us to form it? How, for example, can we imagine an end to space or time? We never saw any object without something beyond it, nor experienced any feeling without something following it. When, therefore, we attempt to conceive the last point of space, we have the idea irresistibly raised of other points beyond it. When we try to imagine the last instant of time, we cannot help conceiving another instant after it Nor is there any necessity to assume, as is done by a modern school of metaphysicians, a peculiar fundamental law of the mind to account for the feeling of infinity inherent in our conceptions of space and time; that apparent infinity is sufficiently accounted for by simpler and universally acknowledged laws.'* * Mill's Logic, vol. 1, pp. 313-17. Thus we stand on the verge of boundless possibility. What truths may yet be discovered in that great and untrodden field, which lies without our experience, no man can tell. All we have yet brought between assertion and proof, is all we have yet conquered, is all that we as yet know, is all that we can yet rely upon. The search after the untried is the highest and apparently the inherent aspiration of roan. The revelation of new worlds continually rewards his noble ambition. At once arrested and allured by the magnificence of nature--we wonder, we work, we wait. CHAPTER V. FACTS We must never forget that accurate and multiplied quantitative facts form the only substantial basis of science.--Parker.