the properties of matter fit it to act and be acted upon in a natural way.

Though matter is not infinitely divisible, yet it is certain it's primordial atoms are indefinitely fmall, fo as to be far beyond the reach of our fenfes. At the fame time our organs are machines, fo exquifitely conftructed, as to be fubject to the impreffions of the fmalleft.

But though the units of matter are fo small as to elude our fenfes, it does not therefore follow, that we can have no certain knowledge of them or of their properties. From the knowledge of concretes, we may clearly difcover what are the general and invariable properties of their conftituent atoms. Every concrete enjoys two kinds of properties: the first are fuch as are infeparable from it as matter, and these properties belong to every atom of which a concrete is compofed; the fecond are fuch as are produced from matter varioufly combined in concretes; the latter are not the original properties, though naturally produced by them. You are therefore to be cautious, left you should afcribe the different properties which matter acquires in a concrete form, unto the original atoms themselves: thus, for inftance, you might as juftly conclude, that the units of which ivory are compofed, are white, as that they are claftic.

OF INERTIA AND GRAVITY.

As I am now going to confider properties that relate to motion, it will be neceffary to proceed with care and circumfpection. "That matter at reft will perfevere for ever in that ftate, unless it be compelled by fome caufe to move," is one of the ideas philofophers have included in the word inertia; and as far as this idea goes, withVOL. III.

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out

out confidering it as a primary property of matter, on account of it's relation to motion, it may be confidered as true.

To the other idea, which is often included in that of inertia, there are many objections, and I think you will hefitate long ere you adopt it. By this we are taught," that any particle of matter, which has been once put in motion, will move on for ever with the fame velocity, unless stopped or refifted." I do not know that any thing can be ftarted more unphilofophical than this notion; a notion which gives to matter an eternal power of changing it's place, in confequence of it's being once difquicted. But leaving every other confideration out of the place, as we do not know whatmotion is in itfelf, it would be a queftion, whether the inertia, here fuppofed, flowed from the nature of matter or motion; a queftion that may be ranked among thofe that are indeterminable. This alone will exclude inertia in the fecond fenfe of the word, from the number of properties.

In the Lectures on Mechanics it is fhewn, that the notion of the vis inertie, in the fecond fenfe, is repugnant to found reafoning, and unfupported by any experimental evidence, and to leffen the effect of prejudice, it is there alfo fhewn, that fome of the firft mathematicians have confeffed, that the vis inertia, confidered in the sense. ufually attributed thereto, must be abandoned.

The reliance obferved in matter, arifes from that certain determination, which all the parts of matter are under, from their fituation and connec tion in the general fyftem; and in confequence of which, they require a force to turn them out of that way, which is appointed to them by the cftablifhed laws of nature. How far any parcel of matter would refift, if it could be taken independent of the present frame of nature, and what

force

force would be requifite in fuch a cafe, to move any given quantity of matter in all directions indifferently, we cannot tell, because we cannot place any matter in fuch a ftate to make a trial.

I must own it appears to me exceeding clear, that no particle of matter can move a fingle inftant, without the prefence of the moving caufe." In this propofition, motion is indeed confidered, not as a mere modification, but as fomething real, and which is always foreign to matter; fo much fo, that matter continually obeys an active caufe, which flows originally from a clafs of beings totally diftinct from that fubflance, which has impenetrability, extent, figure, divifibility, hardness, and inertia in the first fenfe, for it's characteristic properties: a clafs of beings, which are not the object of any of our five fenfes, except by this property of motion, which is perceived by us when it is communicated to matter; but of which we can form no conception, while we have only our five fenfes, or, in other words, while we are deftitute of a fenfe analogous to the cause of motion.

Neither can I perceive any objection to this notion, as it is only the extenfion of another, that I admit in the fulleft and moft abfolute manner, namely, that the first cause of motion neither is nor can be in matter; confequently motion cannot be admitted as a property of matter.

Nor do I conceive how any one could poffibly conceive that motion was effential to matter! How can any thing which has degrees, which may be divided by communication, be confidered as an effential property? If fo, all reafoning on these fubjects is at an end. That, and that only, can be termed an essential property, which is infeparable, even by the imagination, from the fubject to which it is attributed. Every thing elfe is only. phenomenon.

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I fee that matter, in a general fenfe, follows the laws of motion; but then thefe laws belong only to a communicated modification, for they also may be communicated, which is contrary to all notions of an effential or primary property. I feel as intuitively as I do any other axiom, that matter is effentially impenetrable, extended, figured, divifible, and that the atoms thereof may be bard, that every particle at reft perfeveres therein till fomething puts it in motion. But I perceive alfo, with the fame degree of evidence, that the idea of motion may be feparated from that of matter, as eafily as that of any other evident modification. If I must then allow that motion is effential to matter, in order to have the nature of man and the universe explained to me, I would rather choose to be ignorant. And I exhort you to avoid fuch inftructors; knowledge you cannot obtain from them. Let Dinarzade, in the Arabian Tales, amuse herfelf with fictions: but do you feek for truth.

Let us proceed, and by confidering one of the known laws of the motions which prevail in the universe, we shall perceive what further fuppofitions are neceffary to the propofition we are combating. The law to be confidered is that of gravity, by which NEWTON has spread fo much light over the phyfical fyftem of the univerfe. Now among philofophers there are thofe to be found, who confider gravity as an effential property of matter. We will endeavour to difcover what can be meant by fuch a ftrange affertion.

Gravity is that general phenomenon, or that law, in the operations of nature, whereby bodies approach each other; and which acts as far as obfervations have hitherto determined, in the direct ratio of the masses, but inversely as the fquares of the diflances. By it matter is grouped into maffes of different kinds; by it, and a fimple rectilinear

motion,

motion, which is perpetuated, the celeftial orbs revolve in their orbits. This is the law that fome would have us confider as an effential property of

matter.

But who can conceive that a body can a&t where it is not, act without any thing intermediate? To fuppofe that two diftant bodies fhould, without the affiftance of any intermediate fubftance, produce motion in each other, is to invest matter with a power of beginning motion itfelf; a pofition falfe and dangerous, and which has been turned to the purposes of atheism, by a modern philofopher of France. What two particles of matter are at 100,000 leagues, or at the 100,000,000th part of an inch from each other, without any material communication between them; and yet, on account of the one the other is moved!! Again, without any thing happening to one of the particles, let the other be placed at half the distance at which it was before, and they will move towards each other four times quicker! What magic power determines them? What! only because the distance is leffened, which is a mere non-entity, when there is no intermediate agent, the tendency increases, and that accurately in a certain ratio! Let us fhut our books of Speculative philofophy, if they all hold this language; for it is worfe than unintelligible.

It is not eafy to comprehend how thofe philofophers, who reject a fpiritual principle, an immaterial foul in man," because they cannot conceive that a reciprocal action can take place between two fubftances which are not of the fame nature, can, nevertheless, digeft, and allow a reciprocal action between the particles of the moon and those of the earth, without any thing intermediate, but the magical power of the words, GRAVITY is qu ellential property of matter.

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If