Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/55

Book I. which relatively rets in the Ship, will really and abolutely move with the ame velocity which the Ship has on the Earth. But if the Earth alo moves, the true and abolute motion of the body will arie, partly from the true motion of the Earth, in immovable pace; partly from the relative motion of the Ship on the Earth: and if the body moves alo relatively in the Ship; its true motion will arie, partly from the true motion of the Earth, in immovable pace, and partly from the relative motions as well of the Ship on the Earth, as of the Body in the Ship; and from thee relative motions, will arie the relative motion of the Body on the Earth. As if that part of the Earth where the Ship is, was truly mov'd toward the Eat, with a velocity of 10010 parts; while the Ship it elf with a freh gale, and full ails, is carry'd towards the Wet, with a velocity exprs'd by 10 of thoe parts; but a Sailor walks in the Ship towards the East, with 1 part of the aid velocity: then the Sailor will be moved truly and abolutely in immovable pace towards the East with a velocity of 10001 parts, and relatively on the Earth towards the Wet, with a velocity of 9 of thoe parts.

Abolute time, in Atronomy, is ditinguih'd from Relative, by the Equation or correction of the vulgar time. For the natural days are truly unequal, though they are commonly conider'd as equal, and ued for a meaure of time: Atronomers correct this inequality for their more accurate deducing of the celetial motions. It may be, that there is no uch thing as an equable motion, whereby time may be accurately meaured. All motions may be accelerated and retarded, but the True, or equable progres, of Abolute time is liable to no change. The duration or pereverance of the exitence of things remains the ame, whether the Rh