Page:Popular Science Monthly Volume 10.djvu/249

Rh The Rev. Dr. William M. Taylor, in a letter to the Tribune, takes up Prof. Huxley on this ground, and is quite shocked at his logical incapacity. The following is a sample passage from his communication, and a very fair example, besides, of the sort of comment which his lectures have elicited:

The author of this passage is said to be a man of eminence and ability. That may be, but he certainly has not won his distinction either in the fields of logic, astronomy, or biology. When a man undertakes to state the evidence of a theory, and gives us proofs that equally sustain an opposite theory, we naturally conclude that he does not know what he is talking about. This is very much Dr. Taylor's predicament. In trying to contrast the evidence for evolution with the demonstrative proofs of the Copernican theory, he cites facts that are not only as good, but far better, to prove the truth of its antagonist, the Ptolemaic theory.

Dr. Taylor talks as if the Copernican theory is something that anybody can see by looking up into the sky, but the case is far from being so simple. The Copernican theory of the planetary motions assumes that they take place around the sun as their centre; the Ptolemaic theory taught that the earth is the stationary centre of the system, and that the sun, moon, and planets, revolve around it. We must not forget that the Ptolemaic theory was the fundamental conception of astronomy, and guided its scientific development for two thousand years. It was based on extensive, prolonged, and accurate observations; was elucidated and confirmed by mathematics—geometry, and trigonometry; and was verified by confirming the power of astronomic prevision. The planetary motions were traced and resolved on this theory with great skill and correctness, elaborate tables being constructed which represented their irregularities and inequalities, so that their future positions could be foretold, and conjunctions, oppositions, and eclipses, predicted. It embodied a great amount of exact knowledge, and was capable of taking in and preserving all the new results of the labors of a long series of Greek, Latin, Arabian, and modern European astronomers. Dr. Whewell says of it: "In this sense, therefore, the Hipparchian theory was a real and indestructible truth, which was not rejected, and replaced by different truths, but was adopted and incorporated into every succeeding astronomical theory, and which can never cease to be one of the most important and fundamental parts of our astronomical knowledge."

Copernicus, then, did not abolish but rather revised the old astronomy. He accepted the whole system of eccentrics and epicycles, and, so far as planetary motions are concerned, he simply recentred the solar system. He showed that the evidence in favor of that view preponderated, and his theory was a victory of refined, remote, and indirect investigation.