buting (as he well obferves) gravity to fome other caufe diftinct from matter, from atoms, and confequently, from that homogeneous æther or elaftic fluid. The elafticity of which fluid is fuppofed to depend upon, to be defined and measured by it's denfity; and this by the quantity of matter in one particle, multiplied by the number of particles contained in a given space; and the quantity of matter in any one particle or body of a given fize to be determined by it's gravity. Should not therefore gravity feem the original property and firft fuppofed? On the other hand, if force be confidered as prefcinded from gravity and matter, and as existing only in points or centers, what can this amount to but an abstract spiritual incorporeal force? 226. It doth not feem neceffary from the phanomena, to fuppofe any medium more active and fubtil than light or fire. Light being allowed to move at the rate of about ten millions of miles in a minute, what occafion is there to conceive another medium of ftill fmaller and more moveable parts. Light or fire feems the fame with æther. So the ancients understood, and fo the Greek word implies. It pervades all things (a), is every where present.. And this fame fubtil medium according to it's various quantities, motions, and determinations, fheweth itself in different effects or appearances, and is æther, light, or fire. 227. The particles of æther fly afunder with the greatest force, therefore when united they muft (according to the Newtonian doctrine) attract each other with the greateft force; therefore they are acids (b), or conftitute the acid; but this united with earthy parts maketh alkali, as Sir Ifaac teacheth in his tract De acido; alkali, as ap (a) 157. (b) 130. pears pears in cantharides and lixivial falts, is a cauftic; cauftics are fire; therefore acid is fire; therefore æther is fire; and if fire, light. We are not therefore obliged to admit a new medium diftinct from light, and of a finer and more exquifite fubftance, for the explication of phænomena, which appear to be as well explained without it. How can the denfity or elafticity of æther account for the rapid flight of a ray of light from the fun, ftill fwifter as it goes farther from the fun? or how can it account for the various motions and attractions of different bodies? Why oyl and water, mercury and iron repell, or why other bodies attract each other? or why a particle of light fhould repell on one fide and attract on the other, as in the cafe of the Inlandic cryftal? To explain cohesion by hamate atoms is accounted ignotum per ignotius. And is it not as much fo to account for the gravity of bodies by the elasticity of æther? 228. It is one thing to arrive at general laws of nature from a contemplation of the phænomena; and another to frame an hypothefis, and from thence deduce the phænomena. Those who fuppofed epicycles, and by them explained the motions and appearances of the planets, may not therefore be thought to have difcovered principles true in fact and nature. And albeit we may from the premises infer a conclufion, it will not follow, that we can argue reciprocally, and from the conclufion infer the premifes. For instance, fuppofing an elaftic fluid, whofe conftituent minute particles are equidiftant from each other and of equal denfities and diameters, and recede one from another with a centrifugal force which is inverfly as the distance of the centers, and admitting that from fuch fuppofition it must follow, that that the denfity and elaftic force of fuch fluid are in the inverse proportion of the space it occupies when compreffed by any force; yet we cannot reciprocally infer, that a fluid endued with this property must therefore confift of fuch fuppofed equal particles; for it would then follow, that the corftituent particles of air were of equal denfities and diameters; whereas it is certain, that air is an heterogeneous mafs, containing in its compofition an infinite variety of exhalations, from the different bodies which make up this terraqueous globe. 229. The phænomena of light, animal spirit, mufcular motion, fermentation, vegetation, and other natural operations, feem to require nothing more than the intellectual and artificial fire of Heraclitus, Hippocrates, the Stoics (a), ard other ancients. Intellect, fuperadded to ætherial fpirit, fire, or light, moves, and moves regularly, proceeding, in a method as the Stoics, or increafing and diminishing by meafure, as Heraclitus expreffed it. The Stoics held that fire comprehended and included the fpermatic reafons or forms (λógus σTTEQμATIXY's) of all natural things. As the forms of things have their ideal exiftence in the intellect, fo it fhould feem that feminal principles have their natural existence in the light (b), a medium confifting of heterogeneous parts, differing from each other in divers qualities that appear to fenfe, and not improbably having many original properties, attractions, repulfions and motions, the laws and natures whereof are indifcernible to us, otherwife than in their remote effects. And this animated heterogeneous fire fhould feem a more adequate caufe, whereby to explain the phæ (a) 166, 168. (b) 164. O 2 nomena nomena of nature, than one uniform ætherial medium. - 230. Aristotle indeed excepts against the elements being animated. Yet nothing hinders why that power of the foul, ftyled by him T or locomotive, may not refide therein, under the direction of an intellect, in fuch fenfe, and as properly as it is faid, to refide in animal bodies. It must neverthelefs be owned, that albeit that philofopher acknowledgeth a divine force or energy in fire, yet to fay that fire is alive, or that having a foul it fhould not be alive, feem to him equally abfurd. See his fecond book, De partibus animalium. 231. The laws of attraction and repulfion are to be regarded as laws of motion, and these only as rules or methods obferved in the productions of natural effects, the efficient and final caufes whereof are not of mechanical confideration. Certainly, if the explaining a phænomenon be to affign its proper efficient and final caufe (a), it fhould feem the mechanical philofophers never explained any thing; their province being only to difcover the laws of nature, that is the general rules and methods of motion, and to account for particular phænomena by reducing them under, or fhewing their conformity to fuch general rules. 232. Some corpufcularian philofophers of the laft age, have indeed attempted to explain the formation of this world and its phænomena, by a few fimple laws of mechanifm. But if we confider the various productions of nature, in the mineral, vegetable and animal parts of the creation, I believe we fhall fee caufe to affirm, that not any (a) 154, 155, 160. one one of them has hitherto been, or can be accounted for on principles merely mechanical; and that nothing could be more vain and imaginary, than to fuppofe with Defcartes, that merely from a circular motion's being impreffed by the fupreme agent on the particles of extended fubftance, the whole world with all its feveral parts, appurtenances, and phænomena might be produced, by a neceffary confequence from the laws of motion. 233. Others fuppofe that God did more at the beginning, having then made the feeds of all vegetables and animals, containing their folid organical parts in miniature, the gradual filling and evolution of which, by the influx of proper juices, doth constitute the generation and growth of a living body. So that the artificial ftructure of plants and animals daily generated, requires no prefent exercise of art to produce it, having been already framed at the origin of the world, which with all its parts hath ever fince fubfifted going like a clock or machine by itself, according to the laws of nature, without the immediate hand of the artist. But how can this hypothefis explain. the blended features of different fpecies in mules and other mongrels? or the parts added or changed, and fometimes whole limbs loft by marking in the womb? or how can it account for the refurrection of a tree from its ftump, or the vegetative power in its cutting? in which cafes we must neceffarily conceive fomething more than the mere evolution of a feed. 234. Mechanical laws of nature or motion direct us how to act, and teach us what to expect. Where intellect prefides, there will be method and order, and therefore rules, which if not stated and |