and therefore it is unphilosophical, to assume the liberty of imagining that there really does exist more than one cause of the effect.

2. That natural effects of the same kind are to be ascribed to the same cause.

This is a direct consequence of the first rule, and needs only to be explained. Thus the descent of heavy bodies in different parts of the world is to be ascribed to the same cause. Respiration in men and other animals is to be accounted for on the same principles. The reflection of light from different bodies is owing to the same cause.

3. That those qualities of natural bodies which cannot be lessened or augmented in the bodies, on which we can make experiments, are to be deemed the universal properties of all bodies whatsoever. Without this rule we could make no progress in the study of nature. We have no means of knowing the properties of bodies, but by experiments, and from thence drawing conclusions and reasoning by analogy, concerning bodies that are beyond the reach of our examination. The only caution necessary in this case is, that the experiments and observations, from whence we would draw conclusions, be numerous enough; and that pro per regard be paid to the objections that occur. This is the method of induction, which is farther explained by the following precept.

4. That whatsoever is thus collected by induction be received, notwithstanding any conjectural hypothesis to the contrary, until it be contradicted or limited by other more adequate observations on nature.

Mere hypotheses, the figments of a warm imagination, unsupported by observation and experiment, have no place in the newtonian philosophy. Although C

the arguing from induction is no demonstration of general conclusions, yet it is the best that the nature of the thing admits of in many cases, where mathematics cannot be applied. It is not therefore to be rejected, but used with caution, remembering that the degree of evidence it affords is always proportioned to the completeness of the induction.

If we survey the material world by these rules, we shall find that we have no sufficient experiments, to prove that there are different kinds of matter in the universe, but rather that all the diversity, which we observe in natural bodies, arises from the various modifications and different connexions of the same primogenial particles; as all bodies, on which experiments have been made, may be reduced, by a chemical analysis, partly into water, or air, or oil, or earth, or salt: which have therefore been denominated the five elements or principles of all bodies; yet all these original particles of matter have the same common properties.

Matter thus variously modified is found, as far as our experiments reach, to be possessed of these common and universal properties; viz. EXTENSION, SO

LIDITY, FIGURABILITY, DIVISIBILITY, a CAPACI

TY OF MOTION, a vis INERTIÆ, or power of resisting any effort to change its state of motion or rest, ATTRACTION, and REPULSION. These must be explain

ed.

EXTENSION is that property of body, whereby it occupies and fills a certain portion of space, which portion is denominated the place of the body. If this extension lie in one direction it is called a line; if in two, a superficies; and if in three, it is termed a solid. It is this, that constitutes the magnitude of a body: and as all bodies, on which we can make experiments..

☛e evidently possessed of this property, we conclude, by the third and fourth rules of philosophizing, that the stars have this property also; although no experiments confirm it; as our best telescopes leave them without any sensible magnitude, and represent them as shining points. The sensible magnitude which they seem to have to the naked eye is only an optical illusion; and the smallest particles of matter, that float in our atmosphere, are sufficient to hide them for a moment from our view, which by the by occasion their twinkling appearance.

SOLIDITY is that property of body, whereby it excludes every other body out of the same place at the same time. According to this definition, the softest bodies are equally solid with the hardest; as they both equally exclude every other body from the place they Occupy. We acquire the idea of solidity only by the touch, and transfer it to such bodies as we cannot feel. It does not arise from the idea of extension: the image of an object, which has no solidity, appears equally extended with the object itself, and may ap pear also in the same place. Air and water are equally solid with the hardest metals.

FIGURABILITY is that property of body, whereby it is rendered of some particular shape. This quality arises from its limited extension. Since matter cannot be infinite, it must be circumscribed within certain bounds, which determine its figure. Upon this property many important phenomena of nature depend. Different areas and magnitudes may be comprehended under the same lines or superficies. The hardness and softness of bodies depend upon the different figures of the small particles, whereby they may touch in more or fewer points. From this property of body also, we

derive a probable argument for a vacuum. Because it is demonstrable from the principles of geometry, that no assemblage of figures can fill any given space, without any remaining vacuity, but some one or more of the five platonic bodies, viz. the tetrahedron of 4 equal triangular sides, the hexahedron of 6 equal square sides, the octahedron of 8 equal triangular sides, the dodecahedron of 12 equal pentagonal sides, and the icosahedron of 20 equal triangular sides. Now the assertors of a plenum are under the necessity of proving, that, although matter is liable to an infinite variety of forms, yet every particle must be of one or other of the five above mentioned; for otherwise there must of necessity be a vacuum.

DIVISIBILITY is that property of body, whereby its parts are separable from each other. That matter is divisible ad infinitum is capable of being demonstrated various ways. Let a given particle be placed between two parallel lines; and from a given point in one of them let diagonal lines be drawn to the other crossing and dividing the given particle of matter. Now it is evident that the longer these diagonal lines are, the more of the particle will be divided off, and yet that they never can coincide with the parallel line from whence they are drawn, and therefore can never pass through the extremity of the particle and divide it off.

This is true in theory: and in many of the operations of nature and art we observe surprising divisions of matter into its minute parts. What an inconceiv

One grain of gold may be divided into two millions of parts; and a cubic inch into nearly nine billions and five hundred and twenty four millions of parts, each distinctly visible to the naked eye. If a cubic inch were divided into a million of parts, each of

able number of particles flow from an odoriferous body, for many days together, without any sensible diminution of its weight or bulk? How minutely are the particles of tallow divided, that are emitted from a lighted candle in a single vibration? As a candle can be seen at the distance of four miles, the flaming particles of tallow are disseminated through a sphere of eight miles in diameter in an instant. A single grain of copper dissolved in the spirit of sal ammoniac and diluted with water, is thereby divided into many millions of times its own bulk, and tinges the whole. A grain of gold may be beaten into fifty inches square and then divided into two millions of visible parts: and by the help of a microscope which magnifies the diameters of objects but 140 times, this grain may be divided into 40 thousand millions of parts. Nay a grain of gold may be divided into twenty times the number above mentioned, by first gilding the eighth part of an ounce of silver with it, and then drawing it out into a wire of more than seventeen hundred feet long. By the microscope we discover animalcules which lie beyond the reach of the most penetrating eye; the particles of whose circulating juices must be inconceivably small; and yet the particles of light are as much smaller than these, as they are smaller than the whole earth. For otherwise, coming from the sun with

these parts would contain more than two millions of such particles as a single grain of copper might be divided into, and yet all be visible to the naked eye. Nay, if a cubic inch were divided into forty trillions of parts, the particles of some odoriferous bodies would still be less than these. Take the smallest grain of sand that is visible to the naked eye, and it would contain more of the globules that float in the fluids of animalculæ discovered by the microscope, than two hundred and sixty six of the highest mountains in the world would contain of such grains of sand.