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buting (as he well observes) gravity to some other cause distinct from matter, from atoms, and consequently, from that homogeneous æther or clastic fluid. The elasticity of which fluid is supposed to depend upon, to -be defined and measured by it's density; 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 size to be determined by it's gravity. Should not therefore gravity seem the original property and first supposed? On the other hand, if force -be considered as prescinded 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 seem necessary from the phenomena, to suppose any medium more active and subtil than light or fire. Light being allowed to move at the rate of about ten millions of miles in a minute, what occasion is there to conceive another medium of still smaller and more moveabfe ,parts. Light or fire seems the fame with æther. So the ancients understood, and so the Greek word implies. It pervades all things (a), is every where present. And this fame subtil medium according to it's various quantities, motions, and determinations, fheweth itself in disserent efsects or appearances, and is æther, light, or fire.
227. The particles of æther fly asunder with the greatest force, therefore when united they must (according to the Newtonian doctrine) at
, tract each other with the greatest force; therefore they are acids (£), or constitute the acid; but -this united with earthy parts maketh alkali, as sir Ifaac teacheth in his tract de acido; alkali, as ap
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O pears pears in cantharides and lixivial fales, is a caustic, caustics are fire; therefore acid is fire; therefore æther is fire; and if fire, light. We are not therefore obliged to admit a new medium distinct from light, and of a finer and more exquisite substance, for the explication of phænomena, which appear to be as well explained without it. How can the density or elasticity of æther account for the rapid flight of a ray of light from the sun, still swifter as it goes farther from the sun? or how can it account for the various motions and attractions of disserent bodies? Why oyl and water, mercury and iron repell, or why other bodies attract each other? or why a particle of light should repell on one side and attract on the other, as in the case of the Istandic crystal? To explain cohesion by hamate atoms is accounted ignotum per ignotius. And is it not as much so 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 hypothesis, and from thence deduce the phænomena. Those who supposed epicycles, and by them explained the motions and appearances of the planets, may not therefore be thought to have discovered principles true in fact and nature. And albeit we may from the premises inser a conclusion, it will not follow, that we can argue reciprocally, and from the conclusion inser the premises. For instance, supposing an elastic fluid, whose constituent minute particles are equidistant from each other and of equal densities and diameters, and recede one from another with a centrisugal force which is inverfly as the distance of the centers, and admitting that from such supposition it must follow, . that that the density and elastic force of such fluid are in the inverse proportion of the space it occupies when compressed by any force; yet we cannot reciprocally inser, that a fluid endued with this property must therefore consist of such supposed equal particles for it would then follow, that the constituent particles of air were of equal densities and diameters; whereas it is certain, that air is an heterogeneous mass, containing in its composition an infinite variety of exhalations, from the difserent bodies which make up this terraqueous globe.
229. The phænomena of light, animal spirit, muscular motion, sermentation, vegetation, and other natural operations, seem to require nothing more than the intellectual and artificial fire of Heraclitus, Hippocrates, the Stoics (a), and other ancients. Intellect, superadded to ætherial spirit, fire, or light, moves, and moves regularly, proceeding, in a method as the Stoics, or increasing and diminishing by measure, as Heraclitus expressed it. The Stoics held that fire comprehended and included the spermatic reasons or forms (hoyxg o-TTff^a-nw) of all natural things. As the forms of things have their ideal existence in the intellect, so it should seem that seminal principles have their natural existence in the light (b), a medium consisting of heterogeneous parts, difsering from each other in divers qualities that appear to sense, and not improbably having many original properties, attractions, repulsions and motions, the laws and natures whereof are indiscernible to us, otherwise than in their remote efsects. And this animated heterogeneous fire should seem a more adequate cause, whereby to expkin the phæ
(a) 166, 168. (J) 164.
O 2 nomen* nomena of nature, than one uniform ætherial me* dium.
230. Aristotle indeed excepts against the elements being animated. Yet nothing hinders why that power of the foul, styled by him Kihuv., or locomotive, may not reside therein, under the direction of an intellect, in such sense, and as properly as it is faid, to reside in animal bodies. It.must nevertheless be owned, that albeit that philosopher acknowledged a divine force or energy in fire, yet to fay that fire is alive, or that having a foul it should not be alive, seem to him equally absurd. See his second book, De partibus animalium.
. 231. The laws of attraction and repulsion are to be regarded as laws of motion, and these only as rules or methods observed in the productions of natural effects, the efficient and final causes whereof are not of mechanical consideration. Certainly, if the explaining a phænomenon be to assign its proper efficient and final cause (<a), it ihould seem the mechanical philosophers never explained any thing; their province being only to discover the laws of nature, that is the general rules and methods of motion, and to account for particular phænomena by reducing them under, or mewing their conformity to such general rules.
. 232, Some corpuscularian philosophers of the last age, have indeed attempted to explain the formation of this world and its phænomena, by a sew simple laws of mechanism. But if we consider the various productions of nature, in the mineral, vegetable and animal parts of the creation, 1 believe we shall see cause to affirm, that not any
M >S4, »SS, »Goone 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 suppose with Descartes, that merely from a circular motion's being impressed by the supreme agent on the particles of extended substance, the whole world with all its several parts, appurtenances, and phænomena might be produced, by a necessary consequence from the laws of motion.
233. Others suppose that God did more at the beginning, having then made the seeds of all vegetables and animals, containing their solid 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 structure of plants and animals daily generated, requires no present exercise of art to produce it, having been already framed at the origin of the world, which with all its parts hath ever since subsisted 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 hypothesis explain the blended seatures of different species in mules and other mongrels? or the parts added or changed, and sometimes whole limbs lost by marking in the womb? or how can it account for the resurrection of a tree from its stump, or the vegetative power in its cutting? in which cases we must necessarily conceive something more than the mere evolution of a seed.
234. Mechanical laws of nature or motion direct us how to act, and teach us what to expect. Where intellect presides, there will be method and order, and therefore rules, which if not stated