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 Iflandic 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 elafticity 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 recíprocally, and from the conclufion infer the premises. For inftance, fuppofing an elastic fluid, whose constituent 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 density and elastic force of fuch fluid are: in the inverse proportion of the fpace it occupies when compreffed by any force; yet we cannot reciprocally infer, that a fluid endued with this property must therefore confift of such fuppofed equal: particles; for it would then follow, that the conftituent particles of air were of equal denfities and diameters; whereas it is certain, that air is an heterogeneous mass, 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 fpirit, 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), and 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 measure, as Heraclitus expreffed it. The Stoics held that fire comprehended and included the spermatic reafons or forms (λógus σregμatinys) of all natural things. As the forms of things have their ideal existence 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, otherwise than in their remote effects. And this animated heterogeneous fire should seem a more adequate caufe, whereby to explain the phæ (a) 166, 168. O 2 (b) 164. nomera nomena of nature, than one uniform ætherial me dium. 230. Ariftotle indeed excepts against the elements being animated. Yet nothing hinders why that power of the foul, ftyled by him TIN'S 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 nevertheless 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, seem 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 thefe only as rules or methods obferved in the productions of natural effects, the efficient and final caufes whereof are not of mechanical confideration, Certainby, if the explaining a phænomenon be to af fign 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 shall 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 conftitute 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 Jike 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 and conftant would ceafe to be rules. There is therefore a conftancy in things, which is ftyled the courfe of nature (a). All the phænomena in nature are produced by motion. There appears an uniform working in things great and fmall, by attracting and repelling forces. But the particular laws of attraction and repulfion are various. Nor are we concerned at all about the forces, neither can we know or measure them otherwise than by their effects, that is to fay, the motions, which motions only, and not the forces, are indeed in the bodies (b). Bodies are moved to or from each other, and this is performed according to different laws. The natural or mechanic philofopher endeavours to discover those laws by experiment and reafoning. But what is faid of forces refiding in bodies whether attracting or repelling, is to be regarded only as a mathematical hypothefis, and not as any thing really existing in nature. 235. We are not therefore seriously to fuppofe with certain mechanic philofophers, that the minute particles of bodies have real forces or powers by which they act on each other, to produce the various phænomena in nature. The mmute corpufcles are impelled and directed, that is to fay, moved to and from each other according to various rules or laws of motion. The laws of gravity, magnetism, and electricity are divers. And it is not known, what other different rules or laws of motion might be eftablished, by the author of Some bodies approach together, others fly asunder, and perhaps fome others do neither. When falt of tartar flows per deliquium, it is visible that the particles of water floating in the air nature. (a) 160. (6) 155. are |