however, for the taking away fome Prejudices out of Mens Minds, it is very expedient, that we fhould diftinguish thefe Quantities into Abfolute or Relative, True and Apparent, Mathematical and Vulgar, and fo in a Sort defcribe them, which we fhall do in the following Manner.

(2.) TIME Abfolute, True and Mathematical, is an Eternal and Equable Duration, compounded of Parts, fucceeding each other in an immutable Order; for in itfelf, and its own Nature, it flows equably: Nor doth it depend on the Motion of Things, much lefs on their Reft, nor indeed upon their Existence. For whether any Thing were moved or not, whether any Thing did exift, or nothing at all were in being, it would be all one in this Cafe: Time flows equably, whatfoever Relation any other Things have to one another.

(3) RELATIVE Time, or that which is Apparent and Vulgar, is fome fenfible and external Meafure of Duration, (whether it be by Motion, or fome other way; whether it be accurate and even, or uneven;) which is ufed inftead of the true Time, as an Hour, Day, Month, Year, the Duration of the World, or any Syftem from the Beginning to the End, &c. In Aftronomy, Abfolute Time is diftinguifhed from Relative, by the Equation of the Vulgar Time: For the natural Days are unequal, which are nevertheless commonly taken for equal in the meafuring of Time. This Inequality Aftronomers correct, that they may meafure the Heavenly Motions by a truer Time. It is poffible, that there may be no even Motion at all, by which Time may be accurately measured: All Motions may be accelerated and retarded; but the flowing of abfolute Time cannot be changed. The Duration or Perfeverance of the Exiftence of Things is the fame, whether their Motions be fwift, flow, or none at all; confequently, this Duration is justly diftinguished from its fenfible Meafures, and collected from them by Aftronomic Equation. For this is what Aftronomers have labour'd after, namely, that, from the unequal Motions of the Celestial Bodies, they might find an equable Motion about fome Centre, from whence they may more eafily and accurately meafure Duration, that flows equably. (4.) ABSO

(4.) ABSOLUTE, True, and Mathematical Space, is an Extenfion penetrable, indifcerpible, immoveable, infinite, eternal, and every where fimilar to itself; whether or no fuch an Extenfion doth really exift diftinct from Matter, is another Question. But that this is the common Notion of Space, must be allowed, and therefore is to be taken as a Definition. For fo Geometricians do at firft define a Circle, a Square, a Triangle, &c. not troubling themselves with the Queftion, whether fuch Figures do really exift, or no. We ought therefore to lay down fuch a Defcription, of Space before-hand, left afterwards there fhould arife a Strife about Words; that we may afterwards enquire, whether it be the Idea of a Thing really exiftent.

(5.) RELATIVE Space, (which alfo is commonly called Place) is the Meafure of abfolute Space, or any mo veable Dimenfion; which is defined and determined by our Senfes, from its Pofition with refpect to certain Bodies, and is commonly used by the Vulgar for immoveable Space. As the Dimenfion of an Aerial, Celestial or Subterraneous Space, is defined by its Pofition, in refpect of the Earth. Space, abfolute, and relative, are the fame in Species and Magnitude; but do not always remain the fame in Number: That is, if we confider the Space or Cavity contained in any Veffel, whitherfoever the Veffel is moved, the Space or Cavity included in the Sides thereof will always be of the fame Nature, by reafon that Space is every where fimilar to itfelf; and will remain always of the fame Magnitude. becaufe of the given Magnitude of the containing Veffel. But it doth not remain the fame Space numerically, for that is changed perpetually by the Motion of the Veffel. In like manner, if the Earth be moved with an annual Motion about the Sun, the Space of our Air, which relatively, and in refpect of the Earth remains still the fame, that is of the fame Nature and Quantity, will be fometimes one Part of abfolute Space, fometimes another, and fo will be changed perpetually. For indeed, as the Order of the Parts of Time is unchangeable, fo likewife is the Order of the Parts of Space; although the Things which are in them are continually moved and changed. For Times

and

and Spaces are, as it were, the Places of themselves, and of all other Things; which are placed in Time, as to Order of Succeffion, and in Space as to Order of Situation. They are Places by their Effence, and it is abfurd to fay, that the primary Places can be moved. These therefore are the abfolute Places; and the Tranflations, which are from thefe Places, are the only abfolute Motions. But then because the Parts of Space cannot be seen in themselves, or diftinguished from each other by our Senfes, instead of them we ufe fenfible Meafures, defining all Places from the Pofitions of Things, with refpect to fome Body, which we look upon as unmoved, and their Distances from the fame; and eftimating all Motions with Refpect to the faid Places, and fo far as we conceive Bodies to be transferr'd from them. And thus, instead of abfolute Places and Motions, we make ufe of relative; and this indeed not unfitly in common Affairs: But in Philofophical Matters we ought to abstract from the Senfes : For it is poffible, that no Body is really quiefcent, to which Places and Motions may in this Manner be referred.

(6.) A N Abfolute Place is that Part of the abfolute Space which the Body poffeffeth.

(7.) A RELATIVE Place is that Part of Relative Space which a Body poffeffeth. I fay that Place is a Part of Space, not the Situation of a Body, or the ambient Surface, as fome have defined it. For the Place of equal Solids are equal; and the fame Quantity of Matter always poffeffeth the fame Quantity of Space, of whatfoever Figure or Denfity it is. As for Example, the Places of a Sphere, and of a Cube of the fame abfolute Magnitude will be equal, or they will fill and be adequate to equal Places; although the ambient Surfaces, by Reason of the Diffimilitude of the Figures will be uncqual, and fo in all other Figures. Further, the Motion of the Whole is the fame with the Sum of the Motions of all the Parts; that is, the Tranflation of the Whole from its Place is the fame with the Sum or aggregate of the Tranflations of all the Parts from their Places; and confequently, the Place of the Whole is the fame with the Sum of the Places of the Parts, and therefore is internal, and in the whole Body. But Situations, properly fpeaking, have no

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Quantity, and cannot be faid to be greater or leffer, neither are fo much Places as Affections of Places.

(8.) ABSOLUTE Motion is a Tranflation of any Body or Subftance from one abfolute Place, or immoveable Space, into another abfolute Place or immoveable Space. (9.) RELATIVE Motion is a Tranflation of a Body from a relative Place, or fome moveable Space, into fome other relative Place, or moveable Space; or a transferring of a Body from the Neighbourhood of fome ambient Bodies into the Neighbourhood of others; or, laftly, a Tranflation of a Body from its Situation amongst fome certain Bodies into another Situation.

THUS in a Ship, which is under Sail, the relative Place .of a Body is that Part of the Ship in which it is; or that Part of the whole Cavity which fuch a Body fills; and which confequently is moved with the Ship: And the relative Reft of that Body, is the abiding thereof in the fame Part of the Ship, or Cavity. But the true Rest thereof is its Continuance in the fame Part of the immoveable Space. From whence, if the Earth did truly rest, the Body, which relatively retts in the Ship, would be moved truly and abfolutely with the fame Velocity wherewith the Ship is moved on the Earth.

Bur if the Earth be alfo moved, the true and abfolute Motion of the Body will arife, partly from the Motion of the Earth in the unmoved Space; partly from the relative Motions, both of the Earth, and of the Body in the Ship; and from thefe relative Motions will arife a relative Motion of the Body on the Earth. Thus if that Part of the Earth, in which the Ship is, be moved really towards the Eaft with a Velocity of 10010 Parts, and the Ship be carried towards the Weft by the Wind with a Velocity of 10. Parts; and the Mariner walk in the Ship towards the Eaft with 1. Part of Velocity: The Mariner will be moved truly and abfolutely in the unmoved Space towards the Eaft with 10001. Parts of Velocity, and relatively on the Earth towards the Weft with 9. Parts of Velocity.

(10.) THE Quantity of Matter is the Measure of the fame, arifing from the Denfity and the Magnitude thereof conjunctly.

THUS Air, which is as denfe again as fome other Air, and poffeffes double the Space, is fourfold in Quantity to

the

the other. And if a Cubic Veffel contain Air, which by Compreffion is reduced into a leffer Cube, the Denfity in the leffer Cube will be to that in the greater, as the greater Cube is to the lefs; or in the triplicate Proportion of the Sides reciprocally; and the Distances of the Particles of Air which are like, and in like Manner pofited, will be in the Proportion of the Cubic Sides. The fame Thing is to be understood of Snow or Powders condens'd by Compreffion or Liquefaction: And there is the like Reafon of all Bodies in whatever Manner condens'd, We have no Regard in this Place to a Medium pervading the Interftices of the Parts, if there be any fuch: But we fhall call this Quantity of Matter, (which is to be reckon'd from the Denfity and Magnitude conjun&ly) every where hereafter Body or Mafs. And the fame is known by the Weight of every Body; for an equal Quantity of Matter, of what Sort foever it is, doth equally gravitate; as is manifeft by Experiments of Pendulums which have been moft accurately made. And from hence it is certain, that either there is no Etherial Medium pervading the Pores of Bodies; or if there be any, feeing it doth in no wife gravitate nor hinder the Motion of Bodies, it ought to be reckoned Matter differing from that of all other Bodies; yea, in fpeaking properly, it deferves not the Name of Body or Matter at all. But we fhall have Occafion to fay more of this hereafter.

(11.) THE Quantity of Motion is the Meafure of the fame, arifing from the Velocity, and from the Quantity of the Matter conjunctly.

THE Motion of the Whole is the Sum of the Motions of all the Parts; and confequently in a Body double of fome other, and mov'd with equal Velocity, the Motion, is two-fold of the Motion which is in the other Body; and in the double Velocity of the greater Body it is fourfold. The Quantity of Matter therefore is equal to the Rectangle of the Denfity drawn into the Magnitude; and the Quantity of the Motion equal to the Rectangle of the Velocity drawn into the Quantity of the Matter. From which Principle the Forces of Machines are eafily deduced. For where foever in the Equilibrium of Machines a Body is greater, there the Celerity of that Bo

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