Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/44

 same, not to serve for a necessary demonstration, but to adorn a Platonick Conceit; to which I will add another particular observation of our Academick, which hath in it something of admirable. Let us suppose amongst the decrees of the divine Architect, a purpose of creating in the World these Globes, which we behold continually moving round, and of assigning the centre of their conversions; and that in it he had placed the Sun immoveable, and had afterwards made all the said Globes in the same place, and with the intended inclinations of moving towards the Centre, till they had acquired those degrees of velocity, which at first seemed good to the same Divine Minde; the which being acquired, we lastly suppose that they were turned round, each in his Sphere retaining the said acquired velocity: it is now demanded, in what altitude and distance from the Sun the place was where the said Orbs were primarily created; and whether it be possible that they might all be created in the same place? To make this investigation, we must take from the most skilfull Astronomers the magnitude of the Spheres in which the Planets revolve, and likewise the time of their revolutions: from which two cognitions is gathered how much (for example) Jupiter is swifter than Saturne; and being found (as indeed it is) that Jupiter moves more swiftly, it is requisite, that departing from the same altitude, Jupiter be descended more than Saturne, as we really know it is, its Orbe being inferiour to that of Saturne. But by proceeding forwards, from the proportions of the two velocities of Jupiter and Saturne, and from the distance between their Orbs, and from the proportion of acceleration of natural motion, one may finde in what altitude and distance from the centre of their revolutions, was the place from whence they first departed. This found out, and agreed upon, it is to be sought, whether Mars descending from thence to his Orb, the magnitude of the Orb, and the velocity of the motion, agree with that which is found by calculation; and let the like be done of the Earth, of Venus, and of Mercury; the greatness of which Spheres, and the velocity of their motions, agree so nearly to what computation gives, that it is very admirable.

I have hearkened to this conceit with extreme delight; and, but that I believe the making of these calculations truly would be a long and painfull task, and perhaps too hard for me to comprehend, I would make a trial of them.

The operation indeed is long and difficult; nor could I be certain to finde it so readily; therefore we shall refer it to another time, and for the present we will return to our first proposal, going on there where we made digression; which, if I well remember, was about the proving the motion by a right line of no