instances, we are now able to perceive the causes, which prevent an unlimited improvement in those inventions, which seemed to promise fairly for it at first. The original improvers of telescopes would probably think, that as long as the size of the specula, and the length of the tubes could be increased, the powers and advantages of the instrument would increase; but experience has since taught us, that the smallness of the field, the deficiency of light, and the circumstance of the atmosphere being magnified, prevent the beneficial results that were to be expected from telescopes of extraordinary size and power. In many parts of knowledge, man has been almost constantly making some progress; in other parts, his efforts have been invariably baffled. The Savage would not probably be able to guess at the causes of this mighty difference. Our further ex-
