Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/219

 holding fast the stone B to its little wheel, than for the holding the stone C to its great one, which is as much as to say, that such a small thing will impede the extrusion in the great wheel, as will not at all hinder it in the little one. It is manifest therefore that the more the wheel augmenteth, the more the cause of the projection diminisheth.

From this which I now understand, by help of your minute dissertation, I am induced to think, that I am able to satisfie my judgment in a very few words. For equal impetus being impressed on both the stones that move along the tangents, by the equal velocity of the two wheels, we see the great circumference, by means of its small deviation from the tangent, to go seconding, as it were, and in a fair way refraining in the stone the appetite, if I may so say, of separating from the circumference; so that any small retention, either of its own inclination, or of some glutination sufficeth to hold it fast to the wheel. Which, again, is not able to work the like effect in the little wheel, which but little prosecuting the direction of the tangent, seeketh with too much eagernesse to hold fast the stone; and the restriction and glutination not being stronger than that which holdeth the other stone fast to the greater wheel, it * breaks loose, and runneth along the tangent. Therefore I do not only finde that all those have erred, who have believed the cause of the projection to increase according to the augmentation of the vertigo's velocity; but I am further thinking, that the projection diminishing in the inlarging of the wheel, so long as the same velocity is reteined in those wheels; it may possibly be true, that he that would make the great wheel extrude things like the little one, would be forced to increase them as much in velocity; as they increase in diameter, which he might do, by making them to finish their conversions in equal times; and thus we may conclude, that the Earths revolution or vertigo would be no more able to extrude stones, than any little wheel that goeth so slowly, as that it maketh but one turn in twenty four hours.

We will enquire no further into this point for the present: let it suffice that we have abundantly (if I deceive not my self) demonstrated the invalidity of the argument, which at first sight seemed very concluding, and was so held by very famous men: and I shall think my time and words well bestowed, if I have but gained some belief in the opinion of Simplicius, I will not say of the Earths mobility, but only that the opinion of those that believe it, is not so ridiculous and fond, as the rout of vulgar Philosophers esteem it.

The answers hitherto produced against the arguments brought against this Diurnal Revolution of the Earth taken from