ly more than two or three straggling copies will forth with find their way to England. But in 1670-80, the bookseller always imported immediately: and the mathematical bookseller complained that he could not sell more that twenty or thirty, until the book had gained reputation, in a manner which implied that even this state of things was a falling off.
(7) The reader should be aware that both Rheticus and Copernicus propounded the theory of the earth's motion only as an hypothesis, to save appearances: using this phrase in the old sense, though most historians suppose that they also intended the thing signified by its more modern meaning. The phrase to save appearances is a cast off phrase of physics; we now say to explain phenomena. Thus the supposition that the earth turns on its axis preserves the diurnal appearances of the heavens, and makes them follow: and the old explanation does the same. Copernicus contends for the supposition of the earth's motion as the most simple mode of deducting and calculating the celestial phenomena: leaving the question of its actual truth or falsehood open. The utmost extent to which he commits himself on this point is (lib. 1. cap. 8) the affirmation, that on the balance of à priori reasons, the motion of the earth, especially the diurnal motion, is more probable than its stability.
(8) Castiglione, who published Newton's Opuscula, knew that the Optics were published in 1704, and had a copy of 1706. He took for granted (pref. p. vii.) that there could not be two editions so near in time, and therefore announced that by the printer's negligence the edition of 1704 had 1706 on the title page. The fact is that there was an English edition in 1704, and a Latin one in 1706.
[10] (9) Maurolycus, in 1553, recieved a pension expressly to enable him to publish his works: which makes it likely that some of those previous published had been delayed, and the more so as there was re-
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