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hor on the general laws of motion, nor on the den:
241. Gravity and fermentation are received for : two moft extensive principles. From fermentation are derived the motion and warmth of the heart and blood in animals, subterraneous heat, fires, and earthquakes, meteors and changes in the atmo-' sphere. And, that attracting and repelling forces operate in the nutrition and dissolution of animal and vegetable bodies, is the doctrine both of Hip
pocrates and Sir Isaac Newton. : The former of thefe celebrated authors, in his treatise concerning diet or regimen, observes, that in the nourishment of man, . one part tepells and another attracts, And again, in the same treatise, two carpenters, faith he, saw a piece of timber ; one draws, the other pushes; these two actions tend to one and the same end, though in a contrary direction, one up, the other down : This imitates the nature of man : THEữua và Hày. Axoi, xà và cô ta.
242. It is the general maxim of Hippocrates, that. the manner wherein nature acts consisteth in attracting what is meet and good, and in repelling what is disagreeable or hurtful. He makes the whole of the animal economy to be administred by the faculties or powers of nature. Nature alone, faith he, sufficeth for all things to animals. - She knows of herself what is necessary for them. Whence it is plain, he means a conscious intelligent nature, that presides and moves the ætherial fpirit. And tho' he declares all things are accomplished on man by necessity, yet it is not a blind fate or chain of mere corporeal causes, but a divine necessity, as he himself expresly calls it. And what is this but an over-ruling intelligent power that dis, poseth of all things? : 243. Attraction cannot produce, and in that fense account for the phænomena, being it self one of the phænomena produced and to be accounted for (n). Attraction is performed by different laws, and cannot therefore in all cases be the effect of the elasticity of one uniform medium. The phænomena of electrical bodies, the laws, and variations of magnetism, and, not to mention other kinds, even
gravity, is not explained by elasticity, a phænd. menon not less obscure than itself. But then, although it fhews not the agent, yet it fheweth a rule and analogy in nature to say, That the solid parts of animals are endued with attractive powers, whereby from contiguous Auids they draw like to like; and that glands have peculiar powers attractive of peculiar juices (0) Nature seems better known and explained by attractions and repulsions, than by those other mechanical principles of fize, figure, and the like : that is by Sir Isaac Newton, than Descartes. And natural philosophers excel, as they are more or less acquainted with the laws and methods observed by the author of nature,
244. The size and shape of particles and general laws of morion can never explain the secretions without the help of attraction, obscure perhaps as to it's cause, but clear as a law. Numberless in. Atances of this might be given : Lemery the younger thought himself obliged to suppose, the particles of light or fire (contrary to all reason) to be of a very gross kind, even greater than the pores of the burnt limestone, in order to account for their being detained or imprisoned therein; but this phæ. nomenon is easily reduced to attraction. There would be no end of enumerating the like cases, The activity and force of ætherial spirit or fire by the laws of attraction, is imparted to grosser particles (P), and thereby wonderfully supports the peconony of living bodies. By such peculiar com, positions and attractions it seems to be effected, that denser Huids can pass where air itself cannot, (as oil through leather) and therefore through
the nicest and fineft strainers of an animal table.
245. The ancients had some general conception of attracting and repelling powers (9) as natural principles. Galilæi had particularly considered the attraccion of gravity, and made some discovery of the laws thereof. But Sir Isaac Newton by his singuJar penetration, profound knowledge in geometry and mechanics, and great exactness in experiments, hach cast a new light on natural science. The laws of attraction and repulsion were in many instances discovered, and first discovered, by him. He Thewed their general extent, and therewith, as with a key, opened several deep secrets of nature, in the knowledge whereof he seems to have made a greater progress, than all the sects of corpuscularians together had done before him. Nevertheless, the principle of attraction itself is not to be explained by physical or corporeal causes.
246. The Cartesians attempted to explain it by the nisus of a subtil element, receding from the center of its motion, and impelling grosser bodies towards it. Sit Isaac Newton in his later thoughts seems (as was before observed) to have adopted somewhat not altogether foreign from this notion, ascribing that to his elastic medium (r) which Delcartes did to his second element. But the great men of antiquity resolved gravity into the immediate action of an intelligent incorporeal being. To which also Sir Isaac Newton himself attests and subscribes, although he may perhaps sometimes be thought to forget himself, in his manner of speaking of phy. fica] agents, which in a strict sense are none at all and in supposing real forces to exist in bodies, in
which, to speak truly, attraction and repulsion should be considered only as tendencies or motions, that is, as mere effects, and their laws as laws of motion.
247. Though it be supposed the chief business of a natural philosopher to trace out causes from the effects, yet this is to be understood not of agents (s) but of principles, that is, of component parts, in one sense, or of laws or rules, in another. In strict truth all agents are incorporeal, and as such are not properly of physical consideration. The Astronomer, therefore, the Mechanic, or the Chemist, not as such, but by accident only, treat of real causes, agents or efficients. Neither doth it feem, as is supposed by the greatest of mechanical philosophers, that the true way of proceeding in their science is, from known motions in nature to investigate the moving forces. Forasmuch as force is neither corporeal, nor belongs to any corporeal thing (t); nor yet to be discovered by experiments or mathematical reasonings, which reach no farther than difcernible effects, and motions in things passive and moved.
248. Vis or force is to the soul, what extension is to the body, faith saint Augustin, in his tract concerning the quantity of the Soul; and without force there is nothing done or made, and consequently there can be no agent. Authority is not to decide in this case. Ler any one consult his own norions and reason, as well as experience, concerning the origin of motion, and the respective natures, properties, and differences of soul and body, and he will, if I mistake not, evidently perceive, that there is nothing active in the latter. Nor are they natural ) 155. '? () 220.