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INTRODUCTION

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Newtonian Experimental Philosophy.

SECTION I.

PHYSICS.

Containing a Defcription of fuch INSTRU MENTS, PREPARATIONS, and EXPERI MENTS as explain and illuftrate the POWERS of ATTRACTION and REPULSION; the PROPERTIES of natural BODIES, the PRINCIPLES of Mechanic Arts, Chemical OPERATIONS, Nature of METEORS, Doctrine of VEGETATION, MAGNETISM, &c.

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HE Defign of this Courfe of Experimental PHILOSOPHY is to exhibit, in a very natural and eafy Manner, the principal and most important Phænomena or Appearances of natural Bodies; to account for their Caufes and Effects on plain

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and evident Principles, and to prove and illustrate the fame by a great Variety of curious and new-contrived Inftruments and Experiments; fo as to render the Whole not only the most rational and inftructive, but also the most pleasant and fatisfactory

Entertainment.

Plate I.

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2. The Subject of the prefent Lecture are thofe Powers of Nature which may justly esteemed the fundamental Principles of all natural Philofophy; to fhew the Reality of their Existence, their feveral Properties and wonderful Effects, and to apply the fame towards fettling a just Theory of Chemistry, the Animal Oeconomy, Vegetation, the Nature of Meteors; together with the principal Properties of the Magnet, and its Ufe in Navigation.

3. This Power affects all the Particles of Matter, and acts upon them in a two-fold Manner, viz. 1. By caufing them to accede to, or approach each other; and because in this Refpect they seem to draw each other mutually, it is called the Power of Attraction. 2. By causing those Particles, in fome Circumstances, to recede, or fly from each other, it is called Repulfion, or a centrifugal Force.

4. But this Power is in itself one and the fame, and only acts in this different Manner

in different Distances between the ParFig. 1. ticles. Thus a Piece of Iron, touched with the Magnet, held near one End of a Magnetic

Magnetic Needle, will attract it; but applied to the other End, it will repel it. So the small Particles of Matter being nearly in Contact, strongly attract each other, and cohere together; but being feparated by the Action of Heat, or otherwife, they repel and fly from each other, as is evident by many Experi

ments.

5. Now to fhew that the Repulfion of one End of the Needle is not a Confequence of Attraction in the other, as fome pre- Fig. 2. tend, I take a Needle, one half Brafs

and the other Iron, and the fame End is repelled in this as in the common Needle, which Experiment plainly fhews this Repulfion is real and pofitive between the two Bodies.

6. And further, it appears by Experiment, that the fame End of the Needle, which is repelled in one Distance is attracted in another nearer Diftance. And hence it follows, that there is a certain near Distance in which the Particles of Matter attract each other; and which is therefore called the Sphere of Attraction; beyond which the faid Power acts by Repulfion; and fo where Attraction ends there a repulfive Power commences.

7. This attracting Power may be confidered as affecting immediately the original Particles of Matter, and by that means caufing them to adhere or cohere firmly together, and fo qualifying them to form larger Portions of Matter, or Bodies of different Degrees of B 2

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