A grain of leaf gold will cover 50 fquare inches, and contains two millions of vifible parts. But the gold which covers the filver wire, ufed in making gold lace, is fpread over a furface twelve times as great. In making this wire, it is ufual to gild ftrongly a cylindrical bar of filver, and afterwards to draw it into wire, by drawing it fucceffively through holes of different magnitudes, formed in plates of fteel. By this means, the furface is prodigiously augmented; notwithstanding which it remains gilt, fo as to preserve an uniform appearance, even when examined with the microscope. It has been calculated, that a fingle grain of gold would cover a furface thirty yards fquare.

FURTHER CONSIDERATIONS ON ATOMS.

Atoms muft originally fubfift in numbers, which cannot be increased or diminished; it is equally impoffible for many to become one, as it is for an unit to be multiplied: fo that the original number of atoms is as invariable as their fizes. An atom may as foon be reduced to nothing, as two can be made to coalefce into an unchangeable fubftance.

Number is the fundamental bafis of motion and changes in matter. An atom cannot act upon itself, nor communicate action, impreffed intimately to it's fubftance, though ever fo large; but a concrete can and does imprefs it's own inward parts, in a mechanical proportion to the power which acts upon it's furface. If any body, though ever so small, has numerical parts, their cohesion must be mechanical; and nature can do nothing, but what, under certain circumftances, it can undo again. To this purpofe Sir Ifaac New

If attraction be a principle, or primary property of matter, how is it that it can be weakened, fufpended for a time, and even quite destroyed? If it be a power determining matter to matter, as a real effential property, how comes it to be overpowered and destroyed by matter, acting mechanically upon matter, fince fuch action must always be confiftent with, and fubfervient to, it's original properties? Now, the force of fire will fufpend the ftrongest attractions. From all we can understand of the units of which matter is compofed, a mass of them lying together, unacted upon by a mechanical material agency, would neither attract, gravitate, nor take place of one another.

Matter hath a capacity of motion, not an ability to move; neither doth any matter act but fo far as it is acted upon. The trumpet hath a capacity of founding, but never till it is founded; of itself it is dead and filent, and would, if left to itfelf, remain fo for ever. To inveft matter with any innate powers, call them by what names (attraction, &c.) you please, is as contrary to the real nature of matter, as to fuppofe that all trumpets are born with lips and lungs, and breath of their own. A ftringed instrument has the capacity of fending forth all poffible harmony; but it must first be acted upon either by the vibratory motion of the air, or immediately by the hand of the master. Such then is the mobility of matter; it is a capacity of being moved and acted upon, but no motive faculty of any kind with itself.

The operations in nature, as far as we can trace them, are carried on mechanically; and though our fenfes are limited as to the minutie of that mechanism, yet we are certain that matter does exift in fuch forms, as will affure us the mechanifm may go on further than we can defcribe. All

the

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

Though matter is not infinitely divifible, 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 subject to the impreffions of the smallest.

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 discover what are the general and invariable properties of their conftituent atoms. Every concrete enjoy's 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 Jecond are fuch as are produced from matter variously combined in concretes; the latter are not the original properties, though naturally produced by them. You are therefore to be cautious, left you fhould ascribe 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 elaftic.

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 mat

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

To the other idea, which is often included in that of inertia, there are many objections, and E 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 unphilosophical than this notion; a notion which gives to matter an eternal power of changing it's place, in confequence of it's being once difquieted. But leaving every other confide ration out of the place, as we do not know what motion is in itself, 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 inertia, in the second 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, considered in the fenfe ufually attributed thereto, must be abandoned.

The refiftance obferved in matter, arises from that certain determination, which all the parts of matter are under, from their fituation and connection 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 eftablished 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 måtter in all directions indifferently, we cannot tell, because we cannot place any matter in such a state to make a trial.

I must own it appears to me exceeding clear, "that no particle of matter can move a single 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 fubftance, 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 effential 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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