Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/142

 It may, in case the Ship were incorruptible, but the Ship decaying, the Navigation must of necessity come to an end.

But in the Mediterrane, though the Vessel were incorruptible, yet could she not sail perpetually towards Palestina, that Voyage being determined. Two things then are required, to the end a moveable may without intermission move perpetually; the one is, that the motion may of its own nature be indeterminate and infinite; the other, that the moveable be likewise incorruptible and eternal.

All this is necessary.

Therefore you may see how of your own accord you have confessed it impossible that any moveable should move eternally in a right line, in regard that right motion, whether it be upwards, or downwards, is by you your self bounded by the circumference and centre; so that if a Moveable, as suppose the Earth be eternal, yet forasmuch as the right motion is not of its own nature eternall, but most * terminate, it cannot naturally suit with the Earth. Nay, as was said * yesterday, Aristotle himself is constrained to make the Terrestrial Globe eternally immoveable. When again you say, that the parts of the Earth evermore move downwards, all impediments being removed, you egregiously equivocate; for then, on the other side they must be impeded, contraried, and forced, if you would have them move; for, when they are once fallen to the ground, they must be violently thrown upwards, that they may a second time fall; and as to the impediments, these only hinder its arrival at the centre; but if there were a Well, that did passe thorow and beyond the centre, yet would not a cold of Earth passe beyond it, unlesse inasmuch as being transported by its impetus, it should passe the same to return thither again, and in the end there to rest. As therefore to the defending, that the motion by a right line doth or can agree naturally neither to the Earth, nor to any other moveable, whil'st the Universe retaineth its perfect order, I would have you take no further paines about it, but (unlesse you will grant them the circular motion) your best way will be to defend and maintain their immobility.

As to their immoveablenesse, the arguments of Aristotle, and moreover those alledged by your self seem in my opinion necessarily to conclude the same, as yet; and I conceive it will be a hard matter to refute them.

Come we therefore to the second Argument, which was, That those bodies, which we are assured do move circularly, have more than one motion, unlesse it be the Primum Mobile; and therefore, if the Earth did move circularly, it ought to have two motions; from which alterations would follow in the rising and setting of the Fixed Stars: Which effect is not perceived to ensue.