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can system, yet acknowledged an attractive had the satisfaction to perceive, that the sopower in matter.
lation which he had undertaken caly front In France also, we find Ferivat and Ro. curiosity, was applicable to some of the berval, mathematicians of great eminence, most sublime objects in nature. These dismaintaining the same opinion. The latter, coveries gave birth to his celebrated work, in particular, made it the fundamental prin- which has justly immortalized his name, enciple of his system of physical astronomy, titled “Philosophicæ Naturalis Principia which he published in 1644, under the title Mathematica." of " Arist. Samii de Mundi Systema.”
In generalising these researches, he shewDr. Hooke, however, was the person who ed that a projectile may describe any conic conceived the most just and clear notions section whatsoever, by virtue of a force diof the doctrine of gravitation, of any before rected towards its focus, and acting in proNewton; in his work called “ An Attempt portion to the reciprocal sgnares of the disto prove the Motion of the Earth ;” 1674. tances. He also developed the various proHe observes that the hypothesis on which perties of motion in these kinds of curves, he explains the system of the world, is in and deter.nined the necessary conditions, many respects different from all others; and so that the section should be a circle, an elthat it is founded on the following princi- lipse, or an hyperbola, which depend only ples: 1. That all the heavenly bodies have upon the velocity and primitive position of not only an attraction or gravitation to the body, assigning in each case the conic wards their own centres, but that they mu- section which the body would describe. tually attract each other within the sphere He also applied these researches to the of their activity. 2. That all bodies which motion of the satellites and comets, shewing bave a simple or direct motion, continue to that the former move round their primaries, move in a right line, if some force operating and the latter round the stun, according to without incessantly does not constrain them the same law; and he pointed out the to describe a circle, an ellipse, or some means of determining by observation the yther more complicated curve. 3. That at elements of these ellipses. traction is so much the more powerful, as the He also discovered the gravitation of the attracting bodies are nearer to each other.. satellites towards the sun, as well as to
But the precise determination of the laws wards the planets; and that the sun gravi. and limits of the doctrine of attraction, was tates towards the planets and satellites, as reserved for the genius of Newton: in the well as that these gravitate towards each year 1666, he first began to turn his atten- other: and afterwards extending, by anation to this subject, when, to avoid the logy, this property to all bodies, he esta. plague, he had retired from London into blished the principle, that every molecule the country; but, on account of the incor- of matter attracts every body in proportion rectness of the measures of the terrestrial to its mass, and reciprocally as the square meridian, made before this period, he was of the distance from the body attracted. upable to bring his calculations on the sub Having ascertained this principle, he from ject to perfection at first.
it determined, that the attractive force of a Some years afterwards his attention was þody on a point placed without it is the again called to attraction by a letter of Dr. same as if the whole mass were united at Hooke's; and Picard, having about this the centre. He also proved that the rotation time measured a degree of the earth, in of the earth upon its axis must occasion a France, with great exactness, he employed fattening of it about the poles ; which has this measure in his calculations, instead of since been verified by actual measurement: the one he had before used, and found, by and determined the law of the variation of that means, that the moon is retained in the degrees in different latitudes, upon the her orbit by the sole power of gravity, sup- supposition that the matter of the earth was posed to be reciprocally proportional to homogeneous. the squares of the distances.
But, with the exception of what concerns According to this law, he also found, that the elliptical motions of the planets and co. the line described by bodies in their des mets, and the attractions of the heavenly cent is an ellipse, of which the centre of the bodies, these discoveries were not wholly earth occupies one of the foci; and consi- completed by Newton. His theory of the dering afterwards, that the orbits of the pla: figures of the planets is limited by the supnets are in like manner ellipses, having the position of their homogeneity; and his solu. centre of the suu in one of their foci, be ţion of the problem of the precession of the
equinoxes is defective in several respects. gravity ; but it has been supposed that the He has perfectly established the principle other two attractions are confined to two which he had discovered; but left the com or three subtile Auids, which constitute a plete development of its consequences to part of all those bodies that exhibit the the geometers that should succeed him. attractions of magnetism or of electricity.
The profound analysis also, of which he If we compare the different bodies acted was the inventor, bad not been sufficiently on by gravitation, we shall find that the ab. perfected, to enable him to give complete solute force of their gravitation is in all solutions to all the difficult problems which cases the same, provided their distances arise, in considering the theory of the sys- from each other, and their mass be the tem of the world; so that he was oftentimes same ; but this is by no means the case with obliged to give only imperfect sketches or electrical and magnetic bodies : in them the approximations, and leave them to be veri. forces by which they are attracted towards fied by a more rigorous calculation. each other, called electricity and magne
Attractiou may be divided, with respect tism, are exceedingly various, even whien to the law it observes, into two kinds. the mass and the distance are the same. 1. That which extends to sensible distances, Sometimes these forces disappear almost such is the attraction of gravity, of which entirely; at other times they are exceedwe have been treating, which is found in all ingly intense. bodies, and the attraction of magnetism Gravity, therefore, is a force inherent in and of electricity found in some particular bodies; electricity and magnetism not so; bodies; 2. That which extends to very a circumstance which renders the opinion of small, or insensible distances.
their depending on peculiar fluids extremeThe attractions belonging to the first ly probable. If we compare the absolute class must be as numerous as there are bo. force of these three powers with each other, dies situated at sensible distances. It has it would appear that the intensity of the been proved that their intensity varies with two last, every thing else being equal, is the mass and the distance of the attracting greater than that of the first ; but their rebodies ; it increases with the mass of lative intensity cannot be compared, and is those bodies, but diminishes as the distance therefore unknown. Hence it follows that between them increases. The rate of va these different attractions, though they folriation has been demonstrated to be in- low the same laws of riation, are not the versely as the square of the distance in all same in kind. cases of attraction belonging to the first The attractions between bodies at insenclass.
sible distances, have been distinguished by The nature of the attraction of gravity the name of affinity, while the term attrachas been already discussed. It is, as far as tion has been more commonly confined to the experience of man can extend, univer- . cases of sensible distance. sal in all matter. The attractions of mag Affinity may be considered as operating on netism and of electricity are partial, being homogeneous or heterogeneous substances. confined to certain sets of bodies, while Homogeneous affinity urges substances of the rest of matter is destitute of them ; for the same nature together as iron to firon, it is well known that all bodies are not elec- soda to soda. Heterogeneous affinity draws tric, and that scarcely any bodies are mag- substances of different nature into union, as netic, except iron, cobalt, nickel, and chro- acid and alkalis. mium ; and there is good reason to sospect Homegeneous affinity is usually denomithat the magnetism of the three latter sub- nated cohesion, and sometimes adhesion stances is caused by their containing some when the surfaces of bodies are only referred iron united to them.
to; it is nearly universal ; as far as is known, The intensity of these three attractions caloric and light alone are destitute of it. increases as the mass of the attracting bo Heterogeneous affinity is the cause of the dies, and diminishes as the square of the formation of compound substances; thus distance,
muriatic acid unites with soda, and forms The first extends to the greatest distance sea-salt; and sea-salt in saturated solution is at which bodies are known to be separated united into masses by homogeneous affinity.' from each other. How far electricity ex- Heterogeneous affinity is universal as far as tends has not been ascertained ; but mag- is kuown ; that is to say, there is no subnetism extends at least so far as the semi- stance which is not attracted by some other diameter of the earth. All bodies possess substance. It is generally taken for grant
ed, that every substance has more or less af- other band, no proof has ever appeared in finity for all others, though it is certainly as- support of this opinion. suming more than even analogy can war Affinity agrees with sensible attraction in rant, and is a point which we have no means every determinable point: like sensible atof ascertaining
traction, it increases with the mass, and diAffinity, like sensible attraction, varies minishes as the distance augments; consewith the mass and the distance of the attract. quently it is just to conclude, that attraction, ing bodies. That cohesion varies with the mass whether it be sensible or insensible, is in all cannot indeed be ascertained, because we cases, the same kind of force, and regulated have no means of varying the mass without precisely by the same general laws. at the same time altering the distance. But The forces of atfinity, though the same in cases of the adhesion of the surfaces of in kind, and possessing the same rate of vahomogeneous bodies, which is undoubtedly riation with regard to distances, and also in an instance of homogeneous affinity, it respect to the mass, are vastly more numehas been demonstrated that the force of rous than those of sensible attraction; for, adhesion increases with the surface, which instead of three, they amount to as many as in some respect is the same as with the there are heterogeneous bodies. But even
when the distance and the mass are the That heterogeneous affinity increases same, as far as can be judged, the affinity with the mass has been observed long ago of two bodies for a third is not the same. in particular instances, and has been lately Thus barytes has a stronger affinity for suldemonstrated by Berthollet to take place phuric acid than potash has; for, on equal in every case. Thus a given portion of wa- portions of them being mixed with a small ter is retained more obstinately by a large quantity of the acid, the barytes seizes a quantity of sulphuric acid, than by a small much larger proportion of the acid than the quantity. Oxygen is more easily abstract: potash does The difference of intensity ed from oxides which are oxydised to a extends to all substances, for there are maximum, than from those which are oxyded scarcely any two bodies, whose particles to a minimum. Lime only takes off the have precisely the same affinity for a third, greatest part of the carbonic acid from and scarcely any two bodies whose compopotash, which still retains a portion of it; nent parts adhere together with exactly the and salphuric acid does not totally displace same force. phosphoric acid from the lime united to it Because these affinities do not tary in in phosphate of lime, a part of it remains common circumstances, like magnetism and umdisturbed. In these and many other electricity, but are always the same when cases, a small portion of one substance is re other circumstances are equal, it has been tained by a given quantity of another more argued that they do not, like them, depend strongly than a large portion ; and Ber: on peculiar Auids, the quantity of which thollet has shewn, that in all“cases a large may vary ; but that they are permanent quantity of one substance is capable of ab- forces, inherent in every part of the attractstracting a portion of another from a small ing bodies. portion of a third, how weak soever the affi But after the extraordinary discoveries nity between the first and second is, and that have been lately made of the powerful how strong soever that between the second effects which electricity, as excited by the and third.
galvanic apparatus, has in chemical attracThat the force of affinity increases as the tions : and when the great force of the affidistance diminishes, and the contrary, is ob- nity of the bases of potaslı and of soda to vious; for it becomes insensible, whenever oxygen have been overcome by it, we must the distance is sensible, and, on the other hesitate at least in continuing the above hand, it becomes exceedingly great, when opinion; if we do not totally reject it, to the distance is exceedingly diminished. But adopt its reverse, and consider electric fire the particular rate which this variation fol- in future as the great agent of elective afti. lows is still unknown; some have supposed nities. There is no reason why electric fire the rate to be the same as that of sensible may not be subject to the same laws of atattraction, and that its intensity varies in- traction as other substances, and wliy it may versely, as the square of the distance; no not remain united to bodies in a latent or sufficient argument has ever been advanced, inactive state, as well as caloric; we have to prove this law to be incompatible with already shewn, that the mass of any subthe phenomena of affinity; but, on the stance has a powerful effect on its degree
of afinity; many of the effects of electric Judicial astrology, magic, and many other fire on affinity might be explained by this chimeras, cannot be disproved; but, at increased power of it when acting in a mass, least since the great law of truth has been or at farthest by supposing, that its power adopted for philosophy, that no argument increased with its mass in a greater ratio was to be adınitted in it that was not dethan that of other substances.
monstrable by experiment, or by proof It has been judiciously remarked, by a equally satisfactory, mankind has ceased to respectable cliemical writer, that the varia be led astray by them. tion of intensity, which formis so remarka It is now high time either to banish the ble a distinction between affinity and gra- atomic theory into the same regions of oblivitation, may be only apparent, and not vion as the others above mentioned, or to real, and may only arise from the much prove the existence of the atoms on which it nearer approach which the parts of one sub- is founded; but as this is in its nature an im. stance may be capable of, to those of a se. possibility, it is to be hoped that the time is cond, than to those of a third ; and that thus not far distant, when philosophers will cease it may be that barytes attracts sulphuric to confound imaginary beings with real exacid with greater intensity than potash, be. istences, and when all that has been written cause the particles of barytes, when they of atoms, will be in no more esteem than act upon the acid, are at a smaller distance the voluminous treatises de Pygmeis et trom it than the particles of the potash; to Salamandris, which are to be found among which we shall add, that it is possible that the folios of some of our great academical the degree of insensible distance to which the libraries. parts of substances can approach, depends It is true, that the atomic theory accounts on the quantity of latent electric fire com plansibly for many things we otherwise bined with them, or in other words, on the must be content to own are as yet bedegree of their relative attractions to elec- yond our knowledge; this may be a contric fire.
venience to those who wish to impose on This conjecture of the agency of electric the ignorant; but all true lovers of science fire, in elective attractions, has, at least, the will despise so paltry a resource, especially advantage of the atomic theory, which has
when so much is now known, that we need been advanced to account for the same no longer blush to own those points which phenomena, that it relates to matters which are still involved in obscurity, and shew we know really exist, and which are not be the boundaries on the map of science beyond the bounds of hope, indeterminable tween the regions of knowledge and the by experiment. With all due deference to terra incognita of visionary theory. the respectable characters who have used In the above respect of accounting for the atomic theory as an universal explainer, matters unknown, the ideal system of Bi. we beg leave to remind its admirers, that it shop Berkley is equally powerful as, if not is totally inconsistent with the laws of sound superior to, the atomic theory, and has the philosophy, to assume a fact as the basis of advantage over it, of turning our thoughts argument, which itself has never had the incessantly to the Almighty Author of all shadow of proof to support it, and which in things; for which reason, if we must liave its nature is incapable of experiment. It is recourse to improved theories, Berkley's idle, in the present respectable state of very much deserve the preference. science, to talk any more of atoms: as well As to the more minute nature of bodies, inay we again revive the dreams of the an we know that all mineral substances are recients, about the materia subtilis; or those solvable into small laminæ or spicula, of deof Des Cartes, relative to vortices, as to rea terminate shapes, which by their multifa. son of the shape, form, nature, and proper- rious combinations produce the variously ties of atoms, which, from their very defini- formed chrystals, which all mineral bodies tion, are merely visionary, and which, the may be resoived into by art, which most moment we conceive them as having shape, may be made to exliibit by skiltul dissec. lose their essential quality of indivisibility; tion, and which so many shew naturalls. if the existence of atoms cannot be dis- Vegetable substances are resulvable into proved, that is no argument in tavour of small fibres, as are likewise animal subtheir existence, in the way usually supposed; stances for the most part: and from the and the atomic theory las only this property laws of sound philosophy, we must consider in common with every other which lies be. the lamiuæ or spicula, which form the basis yond the reach of our senses.
of crystallization, as the primary parts of
mineral bodies, and fibres as those of or a peacock, of Juno; a caduce, of Mercury; a ganized bodies, until something further can club, of Hercules; and a palm, of Victory. be proved on the subject. These primary ATTRITION, the rubbing or striking of parts of bodies adhere together, it is most bodies one against another, so as to throw probable, by the attraction of cohesion, (as off some of their superficial particles. do also their combinations into crystals and The grinding or polishing of bodies is other forins), modified in some degree by performed by attrition, the effects of which that attraction caused by electric tire. are heat, light, aire, and electricity. The attraction which takes place among
ATTRITION is also often used for the substances in solution is not so easily com friction of such simple bodies as do not prehended; as we know nothing as yet of wear from rubbing against one another, but the exact state in which a substance, capa whose fluids are, by that motion, subjected ble of solidity, exists, when dissolved in a to some particular determination; as the Anid. In our present state of knowledge, various sensations of hunger, pain, and we can only consider it as a fluid itself, ca pleasure, are said to be occasioned by the pable of reassuming a solid form in certain attrition of the organs formed for such imcircumstances.
pressions. The attraction which takes place between AVALANCHES, a name given in Swisbodies in a state of vapour, is similar to that serland and Savoy to those prodigious iu a fuid state; their precise and minute masses of snow which are precipitated, with state in that condition is unknown ; but the
a noise like thunder, and in large torrents, combinations which ensue from the attrac- from the mountains, and which destroy tions of many in both states, are familiar to every thing in their course, and have someall chemists, and from them have proceeded times overwhelmed even whole villages. In many of the most useful substances which 1719 an avalanche from a neighbouring we possess. It is very fortunate for us, glacier overspread the greater part of the however, that if the knowledge of the mi- houses and baths at Leuk, and destroyed a uute and primary state of bodies is, as it considerable number of inhabitants. The were, concealed from our view by an impe. best preservative against their effects being netrable veil, it is not of any very great im
the forests, with which the Alps abound; portance to us; as the effects which bodies there is scarcely a village situated at the produce on each other can be known to us
foot of a mountain that is not sheltered by without it, and it is this latter species of trees; which the inhabitants preserve with knowledge that affords us the dominion uncommon reverence. Thus, what constiover nature, supplies our wants, and forms tutes one of the principal beauties of the the basis of worldly happiness.
country, affords also security to the people. The characteristic marks of affinity may
AVAST, in the sea language a term rebe reduced to the three following:
quiring to stop, to hold, or to stay. 1. It acts only at insensible distances,
AUBLETIA, in botany, so named from and of course affects only the minute parts
M. Aublet, the author of the history of of bodies.
plants in Guiana, a genus of the Polyandria 2. This force is always the same in the Monogynia class and order. Essential chasame substances; but is different in dif. racter, calyx five-leaved ; corolla five-petalferent substances.
led; capsule many celled, echinate, with 3. This difference is considerably modi
many seeds in each cell. There are four, fied by the mass. Thus, though A has a greater
species natives of Guiana.
AUCTIONS, and AUCTIONEERS, every affinity for C than B has, if the mass of B be considerably increased, while that of A
person exercising the trade of an auctioneer, remains unchanged, B becomes capable of for a license ; and without the bills of mor
within the bills of mortality, shall pay 20s. taking a part of C from A.
tality 5s. Auctions and auctioneers are ATTRIBUTES, in logic, are the pre- regulated by several statutes during the dicates of any subject, or what may be present reign. A bidder at an auction, unaffirmed or denied of any thing.
der the usual conditions that the highest ATTRIBUTES, in painting and sculpture, bidder shall be the purchaser, may retract are symbols added to several figures, to his bidding any time before the hammer is intimate their particular office and cha down. racter.
AUCUBA, a genus of the Monoecia Thus the eagle is an attribute of Jupiter; Tetrandria. Essential character, male four.