Of the Laws of Nature. Impious View of being thought Omniscient, or able to account for all Things.

A. I think fo too indeed, good Sir, and ask Pardon for being fometimes too curioufly inquifitive about the Arcana of Na

turę.

B. Sir, we are allowed, yea, 'tis our Duty, to improve our Knowledge, and communicate the fame to each other fo far as we are capable: And having taken this particular Survey of the Properties and Qualities of Bodies; let us proceed to a general View of the Universe composed thereof.

CHA P. XII.

Of Sir ISAAC NEWTON's Laws of

B.

B

Nature.

UT, before we launch out into the boundless Extenfion of the Univerie, where we fhall fee every Thing in Motion all about us; it will be proper previously to confider that (though we have already feen the general Properties and Phænomena of Motion, yet) there are fome stated certain Rules, or Laws, by which all the Motions of all natural Bodies are conftantly

ftantly governed and determined; and by which every Thing relating to Motion may be explained.

A. Pray how many are thofe Laws?

B. Sir Ifaac Newton has laid down three

A. But, pray, if you please, tell me why they are called Sir Ifaac Newton's Laws of Nature?

B. That is more than I can do: Sir Ifaac was not the first Inventor of them, fince if you please, you may fee them in Monfieur Defcarte's Philofophy, which was before Sir Ifaac's appeared.

A. Well, we will fuppofe it then the Effect of a fond Indulgence to a great Man of our own Country; but, pray, what are those Laws.

B. The first is this:

LAW I.

All Bodies continue in their State of Rest, or Motion, uniformly in a right Line, excepting they are obliged to change that State by Forces impreffed.

A. What is the Foundation of this Law?

B. We fee all Bodies, by their Nature, are inactive and incapable of moving themfelves; wherefore, unless they be moved by fome external Agent, they muft neceffarily remain for ever at Reft.

Of the Laws of Nature.

93

A. But why must a Body in Motion, if left to it self, for ever fo continue in a right lined Courfe?

B. We know this by daily Experience; for when any Body is put into Motion, it continues to move in the fame rectilineal Direction, and with the fame Velocity; until the Refiftance of the Air, the Power of its own Gravity, the Make of the Body, or fome other external Caufe, determines it from a right-lined Direction, diminishes its Velocity, and brings it at laft to a State of Reft.

A. If this be the Cafe, pray how comes it to pass that the Sun, Moon, Comets, &c. continue their Motion fo long; have the Regions, through which they move, no Refiftance?

B. The Bodies of the Planets and Comets are vastly great; and the Spaces, through which they move, have fmall Refiftance, by which Means they conferve their Motions the longer.

A. Pray what is the next Law of Nature?

B. The fecond Law is this:

LAW II.

All Change of Motion is proportional to the Power of the moving Force impreffed; and is always made according to the right Line in which that Force is impreffed. A. What

A. What do you obferve from thence?

B. That if any Power produceth any Mo tion; another Power which is double, triple, &c. will produce a double, triple, &c. Quantity of Motion; whether it be impreffed together, and at once, or fucceffively by Degrees: And this Motion (because it is ever determined towards the fame Part with the generating Force) is added to the Motion of a Body in the fame Direction by Impact, and it will move so much the quicker; but it is fubtracted from the Motion of a Body in contrary Direction, and therefore that Body will move so much the flower. It is alfo obliquely joined to the Motion of a Body obliquely moving, and will be compounded with it according to the Determination of both. Hence a very confiderable Confequence will follow.

A. Pray what is that?

B. Why, according to the prefent Conftitution of Things, it follows from this Law, there can be no perpetual Motion 3 for by this Law, the Motion produced is but proportional to the generating Force; and all Motions on this Globe being performed in a refifting Medium, viz. the Air, a confiderable Quantity of the Motion muft, in the Communication, be spent on this Medium; and confequently 'tis impoffible the fame Quantity fhould return undiminished upon the first Mover, which

yet,