Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/442

 that I fear I shall have but a small part of it left free and disingaged, to apply to the principal matter that is treated of, and which of it self is but even too obscure and intricate: So that I intreat you to vouchsafe me, having once dispatcht the business of the ebbings and flowings, to do this honour to my house (and yours) some other dayes, and to discourse upon the so many other Problems that we have left in suspence; and which perhaps are no less curious and admirable, than this that hath been discussed these dayes past, and that now ought to draw to a conclusion.

.I shall be ready to serve you, but we must make more than one or two Sessions; if besides the other questions reserved to be handled apart, we would discusse those many that pertain to the local motion, as well of natural moveables, as of the rejected: an Argument largely treated of by our Lyncean Accademick. But turning to our first purpose, where we were about to declare, That the bodies moving circularly by a movent virtue, which continually remaineth the same, the times of the circulation were prefixt and determined, and impossible to be made longer or shorter, having given examples, and produced experiments thereof, sensible, and feasible, we may confirm the same truth by the experiences of the Celestial motions of the Planets; in which we see the same rule observed; for those that move by greater Circles, confirm longer times in passing them. A most pertinent observation of this we have from the Medicæan Planets, which in short times make their revolutions about Jupiter: Insomuch that it is not to be questioned, nay we may hold it for sure and certain, that if for example, the Moon continuing to be moved by the same movent faculty, should retire by little and little in lesser Circles, it would acquire a power of abreviating the times of its Periods, according to that Pendulum, of which in the course of its vibrations, we by degrees shortned the cord, that is contracted the Semidiameter of the circumferences by it passed. Know now that this that I have alledged an example of it in the Moon, is seen and verified essentially in fact. Let us call to mind, that it hath been already concluded by us, together with Copernicus, That it is not possible to separate the Moon from the Earth, about which it without dispute revolveth in a Moneth: Let us remember also that the Terrestrial Globe, accompanyed alwayes by the Moon, goeth along the circumference of the Grand Orb about the Sun in a year, in which time the Moon revolveth about the Earth almost thirteen times; from which revolution it followeth, that the said Moon sometimes is found near the Sun; that is, when it is between the Sun and the Earth, and sometimes much more remote, that is, when the Earth is situate between