Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/267

 case, which Copernicus alledgeth, that by reason this motion is natural to the Earth and not violent, it worketh contrary effects to violent motions; and that those things dissolve and cannot long subsist, to which impulse is conferred, but those so made by nature do continue in their perfect disposure; this answer sufficeth not, I say, for it is overthrown by that of ours. For the animal is a natural body, and not made by art, and its motion is natural, deriving it self from the soul, that is, from an intrinsick principle; and that motion is violent, whose beginning is without, and on which the thing moved conferreth nothing; however, if the animal continueth its motion any long time, it grows weary, and also dyeth, if it obstinately strive to persist therein. You see then that in nature we meet on all sides with notions contrary to the Copernican Hypothesis, and none in favour of it. And for that I have nothing more wherein to take the part of this Opponent, hear what he produceth against Keplerus (with whom he disputeth) upon that argument, which the said Kepler bringeth against those who think it an inconvenient, nay impossible thing, to augment the Starry Sphere immensely, as the Copernican Hypothesis requireth. Kepler therefore instanceth, saying: Difficilius est, accidens præter modulum subjecti intendere, quàm subjectum sine accidente augere. Copernicus ergo verisimilius facit, qui auget Orbem Stellarum fixarum absque motu, quam Ptolomæus, qui auget motum fixarum immensâ velocitate. [Which makes this English.] Its harder to stretch the accident beyond the model of the subject than to augment the subject without the accident. Copernicus hath more probability on his side, who encreaseth the Orb of the fixed Stars without motion, than Ptolomy who augmenteth the motion of the fixed Stars to an immense degree of velocity. Which objection the Author answereth, wondering how much Kepler deceived himself, in saying, that in the Ptolomaick Hypothesis the motion encreaseth beyond the model of the subject, for in his judgment it doth not encrease, save onely in conformity to the model, and that according to its encreasement, the velocity of the motion is augmented. Which he proveth by supposing a machine to be framed, that maketh one revolution in twenty four hours, which motion shall be called most slow; afterwards supposing its semidiameter to be prolonged, as far as to the distance of the Sun, its extreme will equal the velocity of the Sun; and it being continued out unto the Starry Sphere, it will equal the velocity of the fixed Stars, though in the circumference of the machine it be very slow. Now applying this consideration of the machine to the Starry Sphere, let us imagine any point in its semidiameter, as neer to the centre as is the semidiameter of the machine; the same motion that in the Starry Sphere is exceeding