Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/429

 without diminishing or increasing it according to the precise rate of its diminishing or increasing in its Vessel. Because therefore that in the conservation and retention of the impetus before conceived, the disobedience to a new augmentation or diminution of motion consisteth, that moveable that shall be most apt for such a retention, shall be also most commodious to demonstrate the effect that followeth in consequence of that retention. Now how much the Water is disposed to maintain such a conceived agitation; though the causes cease that impress the same, the experience of the Seas extreamly disturbed by impetuous Winds sheweth us; the Billows of which, though the Air be grown calm, and the Wind laid, for a long time after continue in motion: As the Sacred Poet pleasantly sings,

And that long continuing rough after a storm, dependeth on the gravity of the water: For, as I have elsewhere said, light bodies are much easier to be moved than the more grave, but yet are so much the less apt to conserve the motion imparted, when once the moving cause ceaseth. Whence it comes that the Aire, as being of it self very light and thin, is easily mov'd by any very small force, yet it is withall very unable to hold on its motion, the Mover once ceasing. Therefore, as to the Aire which environs the Terrestrial Globe, I would faysay [sic], that by reason of its adherence, it is no lesse carried about therewith then the Water; and especially that part which is contained in its vessels; which vessels are the valleys enclosed with Mountains. And we may with much more reason affirm that this same part of the Air is carried round, and born forwards by the rugged parts of the Earth, than that the higher is whirl'd about by the motion of the Heavens, as ye Peripateticks maintain.

What hath been hitherto spoken, seems to me a sufficient answer to the allegation of Simplitius; yet nevertheless with a new instance and solution, founded upon an admirable experiment, I will superabundantly satisfie him, and confirm to Sagredus the mobility of the Earth. I have told you that the Air, and in particular that part of it which ascendeth not above the tops of the highest Mountains, is carried round by the uneven parts of the Earths surface: from whence it should seem, that it must of consequence come to passe, that in case the superficies of the Earth were not uneven, but smooth and plain, no cause would remain for drawing the Air along with it, or at least for revolving it with so much uniformity. Now the surface of this our Globe, is not all craggy and rugged, but there are exceeding great tracts very