To Astronomy, on the other hand, the pupils of Euclid turned naturally, as to the science which required the greatest amount of their favourite geometry: but even that they were content to let pass from its inductive to its deductive stage—not as we have done now, after two centuries of inductive search for the true laws, and their final discovery by Kepler and Newton: but as soon as Hipparchus had propounded any theory which would do instead of the true laws, content there to stop their experiments, and return to their favourite work of commenting, deducing, spinning notion out of notion, _ad infinitum_.
Still, they were not all of this temper. Had they been, they would have discovered, not merely a little, but absolutely nothing. For after all, if we will consider, induction being the right path to knowledge, every man, whether he knows it or not, uses induction, more or less, by the mere fact of his having a human reason, and knowing anything at all; as M. Jourdain talked prose all his life without being aware of it.
Aristarchus is principally famous for his attempt to discover the distance of the sun as compared with that of the moon. His method was ingenious enough, but too rough for success, as it depended principally on the belief that the line bounding the bright part of the moon was an exact straight line. The result was of course erroneous. He concluded that the sun was 18 times as far as the moon, and not, as we now know, 400; but his conclusion, like his conception of the vast extent of the sphere of the fixed stars, was far enough in advance of the popular doctrine to subject him, according to Plutarch, to a charge of impiety.
Eratosthenes, again, contributed his mite to the treasure of human science—his one mite; and yet by that he is better known than by all the volumes which he seems to have poured out, on Ethics, Chronology, Criticism on the Old Attic Comedy, and what not, spun out of his weary brain during a long life of research and meditation. They have all perished,—like ninety-nine hundredths of the labours of that great literary age; and perhaps the world is no poorer for the loss. But one thing, which he attempted on a sound and practical philosophic method, stands, and will stand for ever. And after all, is not that enough to have lived for? to have found out one true thing, and, therefore, one imperishable thing, in one’s life? If each one of us could but say when he died: “This one thing I have found out; this one thing I have proved to be possible; this one eternal fact I have rescued from Hela, the realm of the formless and unknown,” how rich one such generation might make the world for ever!