« AnteriorContinuar »
from a porous body, (such as wood, bone, parch- that which is opposed to the motion of lesser conment, and the like,) the thicker parts are drawn gregation, by which bodies, with a kind of anti together, and united with a greater effort, and in-pathy, avoid and disperse, and separate them. duration or desiccation is the consequence; and this we attribute not so much to the motion of connexion, (in order to prevent a vacuum,) as to this motion of friendship and union.
selves from, or refuse to unite themselves with others of a hostile nature. For, although this may sometimes appear to be an accidental motion, necessarily attendant upon that of the lesser congregation, because the homogeneous parts cannot unite, unless the heterogeneous be first removed and excluded; yet it is still to be classed separately, and considered as a distinct species, because, in many cases, the desire of avoidance
It is very conspicuous in the excrements of animals, nor less, perhaps, in objects odious to particular senses, especially the smell and taste. For a fetid smell is rejected by the nose, so as to produce a sympathetic motion of expulsion at the mouth of the stomach; a bitter and rough taste is rejected by the palate or throat, so as to produce a sympathetic concussion and shivering of the head. This motion is visible also in other cases. Thus it is observed in some kinds of antiperistasis, as in the middle region of the air, the cold of which appears to be occasioned by the rejection of cold from the regions of the heavenly bodies; and also in the heat and combustion observed in subterraneous spots, which appear to be owing to the rejection of heat from the centre of the
Union from a distance is rare, and yet is to be met with in more instances than are generally observed. We perceive it when one bubble dissolves another, when medicines attract humours from a similarity of substance, when one string moves another in unison with it on different in-appears to be more marked than that of union. struments, and the like. We are of opinion that this motion is very prevalent also in animal spirits, but are quite ignorant of the fact. It is, however, conspicuous in the magnet, and magnetized iron. Whilst speaking of the motions of the magnet, we must plainly distinguish them, for there are four distinct powers or effects of the magnet which should not be confounded, although the wonder and astonishment of mankind has classed them together. 1. The attraction of the magnet to the magnet, or of iron to the magnet, or of magnetized iron to iron. 2. Its polarity towards the north and south, and its variation. 3. Its penetration through gold, glass, stone, and all other substances. 4. The communication of power from the mineral to iron, and from iron to iron, without any communication of the sub-earth. For heat and cold, when in small quantistances. Here, however, we only speak of the ties, mutually destroy each other, whilst in larger first. There is also a singular motion of attrac- quantities, like armies cqually matched, they retion between quicksilver and gold, so that the move and eject each other in open conflict. It is gold attracts quicksilver even when made use of said, also, that cinnamon and other perfumes in ointment, and those who work surrounded by retain their odour longer when placed near privies the vapours of quicksilver are wont to hold a and foul places, because they will not unite and piece of gold in their mouths, to collect the exha-mix with stinks. It is well known that quicklations, which would otherwise attack the heads silver, which would otherwise reunite into a comand bones, and this piece soon grows white.*plete mass, is prevented from so doing by man's Let this suffice for the motion of lesser congregation.
Let the ninth be the magnetic motion, which although of the nature of that last mentioned, yet, when operating at great distances, and on great masses, deserves a separate inquiry, especially if it neither begin in contact, as most motions of congregation do, nor end by bringing the substances into contact, as all do, but only raise them, and make them swell without any further effect. For if the moon raise the waters, or cause moist substances to swell, or if the starry sphere attract the planets towards their apogees, or the sun confine the planets Mercury and Venus to within a certain distance of his mass; these motions do not appear capable of being classed under either of those of congregation, but to be, as it were, intermediately and imperfectly congregative, and thus to form a distinct species.
spittle, pork, lard, turpentine, and the like, from the little affinity of its parts with those substances, so that when surrounded by them it draws itself back, and its avoidance of these intervening obstacles is greater than its desire of reuniting itself to its homogeneous parts; which is what they term the mortification of quicksilver. Again, the difference in weight of oil and water is not the only reason for their refusing to mix, but it is also owing to the little affinity of the two, for spirits of wine, which are lighter than oil, mix very well with water. A very remarkable instance of the motion in question is seen in nitre, and crude bodies of a like nature, which abhor flame, as may be observed in gunpowder, quicksilver, and gold. The avoidance of one pole of the magnet by iron is not, (as Gilbert has well observed,) strictly speaking, an avoidance, but a conformity, or attraction to a more convenient
Let the tenth motion be that of avoidance, or situation.
+ Observe this approximation to Newton's theory'
Let the eleventh motion be that of assimilation, or self-multiplication, or simple generation, by
Let the twelfth motion be that of excitement, which appears to be a species of the last, and is sometimes mentioned by us under that name. It is, like that, a diffusive, communicative, transitive, and multiplying motion; and they agree remarkably in their effect, although they differ in their mode of action, and in their subject-matter. The former proceeds imperiously, and with au
be converted and changed into the assimilating body. The latter proceeds by art, insinuation, and stealth, inviting and disposing the excited towards the nature of the exciting body. The former both multiplies and transforms bodies and substances; thus a greater quantity of flame air, spirit, and flesh is formed; but in the latter, the powers only are multiplied and changed, and heat, the magnetic power, and putrefaction, in the above instances, are increased. Heat does
which latter term we do not mean the simple | motions, bodies appear to aim at the mere pregeneration of integral bodies, such as plants or servation of their nature, whilst in this they atanimals, but of homogeneous bodies. By this tempt its propagation. motion homogeneous bodies convert those which are allied to them, or, at least, well disposed and prepared, into their own substance and nature. Thus flame multiplies itself over vapours and oily substances, and generates fresh flame; the air over water and watery substances multiplies itself and generates fresh air; the vegetable and animal spirit, over the thin particles of a watery or oleaginous spirit contained in its food, multi-thority; it orders and compels the assimilated to plies itself and generates fresh spirit; the solid parts of plants and animals, as the leaf, flower, the flesh, bone, and the like, each of them assimilate some part of the juices contained in their food, and generate a successive and daily substance. For let none rave with Paracelsus, who (blinded by his distillations) would have it, that nutrition takes place by mere separation, and that the eye, nose, brain, and liver, lie concealed in bread and meat, the root, leaf, and flower, in the juice of the earth; asserting that just as the ❘ not diffuse itself, when heating other bodies, by artist brings out a leaf, flower, eye, nose, hand, foot, and the like, from a rude mass of stone or wood, by the separation and rejection of what is superfluous; so the great artist within us brings out our several limbs and parts by separation and rejection. But to leave such trifling, it is most certain that all the parts of vegetables and animals, as well the homogeneous as organic, first of all attract those juices contained in their food, which are nearly common, or at least not very different, and then assimilate and convert them into their own nature. Nor does this assimilation, or simple generation, take place in animated bodies only, but the inanimate also participate in the same property, (as we have observed of flame and air,) and that languid spirit, which is contained in every tangible animated substance, is perpetually working upon the coarser parts, and converting them into spirit, which afterwards is exhaled, whence ensues a diminution of weight, and a desiccation of which we have spoken elsewhere.* Nor should we, in speaking of assimilation, neglect to mention the accretion which is usually distinguished from aliment, and which is observed when mud grows into a mass between stones, and is converted into a stony substance, and the scaly substance round the teeth is converted into one no less hard than the teeth themselves; for we are of opinion that there exists in all bodies a desire of assimilation, as well as of uniting with homogeneous masses. Each of these powers, however, is confined, although in different manners, and should be diligently investigated, because they are connected with the revival of old age. Lastly, it is worthy of observation, that in the nine preceding
See the citing instances, Aphorism 40.
any communication of the original heat, but only by exciting the parts of the heated body to that motion which is the form of heat, and of which we spoke in the first vintage of the nature of heat. Heat, therefore, is excited much less rapidly and readily in stone or metal, than in air, on account of the inaptitude and sluggishness of those bodies in acquiring that motion, so that it is probable that there may be some substances, towards the centre of the earth, quite incapable of being heated, on account of their density, which may deprive them of the spirit by which the motion of excitement is usually commenced. Thus, also, the magnet creates in the iron a new disposition of its parts, and a conformable motion, without losing any of its virtue. So the leaven of bread, yeast, rennet, and some poisons, excite and invite successive and continued motion in dough, beer, cheese, or the human body; not so much from the power of the exciting, as the predisposition and yielding of the excited body.
Let the thirteenth motion be that of impression, which is also a species of motion of assimilation, and the most subtile of diffusive motions. We have thought it right, however, to consider it as a distinct species, on account of its remarkable difference from the two last. For the simple motion of assimilation transforms the bodies themselves, so that if you remove the first agent, you diminish not the effect of those which succeed; thus, neither the first lighting of flame, nor the first conversion into air, are of any importance to the flame or air next generated. So, also, the motion of excitement still continues for a considerable time after the removal of the first agent. as in a heated body on the removal of the original heat, in the excited iron on the removal of the magnet, and in the dough on the removal of the
leaven. But the motion of impression, although diffusive and transitive, appears, nevertheless, to depend on the first agent, so that, upon the removal of the latter, the former immediately fails and perishes; for which reason also it takes effect in a moment, or at least a very short space of time. We are wont to call the two former motions the motions of the generation of Jupiter, because when born they continue to exist; and the latter, the motion of the generation of Saturn, because it is immediately devoured and absorbed. It may be seen in three instances; 1. In the rays of light; 2. In the percussions of sounds; 3. In magnetic attractions as regards communication. For, on the removal of light, colours and all its other images disappear, as, on the cessation of the first percussion and the vibration of the body, sound soon fails; and although sounds are agitated by the wind, like waves, yet it is to be observed, that the same sound does not last during the whole time of the reverberation. Thus, when a bell is struck, the sound appears to be continued for a considerable time, and one might easily be led into the mistake of supposing it to float and remain in the air during the whole time, which is most erroneous. For the reverberation is not one identical sound, but the repetition of sounds; which is made manifest by stopping and confining the sonorous body; thus, if a bell be stopped and held tightly, so as to be immovable, the sound fails, and there is no further reverberation; and if a musical string be touched after the first vibration, either with the finger, (as in the harp,) or a quill, (as in the harpsichord,) the sound immediately ceases. If the magnet be removed, the iron falls. The moon, however, cannot be removed from the sea, nor the earth from a heavy falling body, and we can, therefore, make no experiment upon them, but the case is the same.
may be put, for it must also revolve round certain poles, and why should they be placed where they are, rather than elsewhere? The polarity and variation of the needle come under our present head. There is also observed in both natural and artificial bodies, especially solids rather than fluids, a particular collocation and position of parts, resembling hairs or fibres, which should be diligently investigated, since, without a discovery of them, bodies cannot be conveniently controlled or wrought upon. The eddies observable in liquids by which, when compressed, they successively raise different parts of their mass before they can escape, so as to equalize the pressure, is more correctly assigned to the motion of liberty.
Let the fifteenth motion be that of transmission, or of passage, by which the powers of bodies are more or less impeded or advanced by the medium, according to the nature of the bodies and their effective powers, and also according to that of the medium. For one medium is adapted to light, another to sound, another to heat and cold, another to magnetic action, and so on with regard to the other actions.
Let the sixteenth be that which we term the royal or political motion, by which the predominant and governing parts of any body check, subdue, reduce, and regulate the others, and force them to unite, separate, stand still, move, or assume a certain position, not from any inclination of their own, but according to a certain order, and as best suits the convenience of the governing part, so that there is a sort of dominion and civil government exercised by the ruling part over its subjects. This motion is very conspicuous in the spirits of animals, where, as long as it is in force, it tempers all the motion of the other parts. It is found in a less degree in other bodies, as we have observed in blood and urine, which are not Let the fourteenth motion be that of configura- decomposed until the spirit, which mixed and tion or position, by which bodies appear to desire retained their parts, has been emitted or extina peculiar situation, collocation, and configuration guished. Nor is this motion peculiar to spirits with others, rather than union or separation. This only, although in most bodies the spirit predomiis a very abstruse motion, and has not been well nates, owing to its rapid motion and penetration; investigated; and, in some instances, appears to for the grosser parts predominate in denser booccur almost without any cause, although we be dies, which are not filled with a quick and active mistaken in supposing this to be really the case. spirit, (such as exists in quicksilver or vitriol,) For if it be asked, why the heavens revolve from so that unless this check or yoke be thrown off east to west, rather than from west to east, or why by some contrivance, there is no hope of any they turn on poles situated near the Bears, rather transformation of such bodies. And let not any than round Orion or any other part of the heaven, one suppose that we have forgotten our subject, such a question appears to be unreasonable, since because we speak of predominance in this clasthese phenomena should be received as determi-sification of motions, which is made entirely nate, and the objects of our experience. There with the view of assisting the investigation of are, indeed, some ultimate and self-existing phe- wrestling instances, or instances of predominomena in nature, but those which we have just mentioned are not to be referred to that class: for we attribute them to a certain harmony and consent of the universe, which has not yet been properly observed. But if the motion of the earth from west to east be allowed, the same question
nance. For we do not now treat of the general predominance of motions or powers, but of that of parts in whole bodies, which constitutes the particular species here considered.
Let the seventeenth motion be the spontaneous motion of revolution, by which bodies having a
tendency to move, and placed in a favourable situation, enjoy their peculiar nature, pursuing themselves and nothing else, and seeking as it were to embrace themselves. For bodies seem either to move without any limit, or to tend towards a limit, arrived at which, they either revolve according to their peculiar nature, or rest. Those which are favourably situated, and have a tendency to motion, move in a circle with an eternal and unlimited motion; those which are favourably situated and abhor motion, rest. Those which are not favourably situated move in a straight line, (as their shortest path,) in order to unite with others of a congenial nature. This motion of revolution admits of nine differences; 1. With regard to the centre about which the bodies move; 2. The poles round which they move; 3. The circumference or orbit relatively to its distance from the centre; 4. The velocity or greater or less speed with which they revolve; 5. The direction of the motion, as from east to west, or the reverse; 6. The deviation from a perfect circle, by spiral lines at a greater or less distance from the centre ; 7. The deviation from the circle by spiral lines at a greater or less distance from the poles; 8. The greater or less distance of these spirals from each other; 9. And, lastly, the variation of the poles, if they be movable; which, however, only af- | fects revolution when circular. The motion in question is, according to common and long received opinion, considered to be that of the heavenly bodies. There exists, however, with regard to this, a considerable dispute between some of the ancients as well as moderns, who have attributed a motion of revolution to the earth. A much more reasonable controversy, perhaps, exists, (if it be not a matter beyond dispute,) whether the motion in question (on the hypothesis of the earth's being fixed) is confined to the heavens, or rather descends and is communicated to the air and water. The rotation of missiles, as in darts, musket balls, and the like, we refer entirely to the motion of liberty.
Let the eighteenth motion be that of trepidation, to which (in the sense assigned to it by astronomers) we do not give much credit; but in our serious and general search after the tendencies of natural bodies, this motion occurs and appears worthy of forming a distinct species. It is the motion of an (as it were) eternal captivity; when bodies, for instance, being placed not altogether according to their nature, and yet not exactly ill, constantly tremble, and are restless, not contented with their position, and yet not daring to advance. Such is the motion of the heart and the pulse of animals, and it must necessarily occur in all bodies which are situated in a mean state, between conveniences and inconveniences; so that being removed from their proper position, they strive to escape, are repulsed, and again continue to make the attempt.
Let the nineteenth and last motion be one which can scarcely be termed a motion, and yet is one; and which we may call the motion of repose, or of abhorrence of motion. It is by this motion that the earth stands by its own weight, whilst its extremes move towards the middle, not to an imaginary centre, but in order to unite. It is owing to the same tendency, that all bodies of considerable density abhor motion, and their only tendency is not to move, which nature they preserve, although excited and urged in a variety of ways to motion. But if they be compelled to move, yet do they always appear anxious to recover their former state, and to cease from motion, in which respect they certainly appear active, and attempt it with sufficient swiftness and rapidity, as if fatigued and impatient of delay. We can only have a partial representation of this tendency, because with us every tangible substance is not only not condensed to the utmost, but even some spirit is added, owing to the action and concocting influence of the heavenly bodies.
We have now, therefore, exhibited the species or simple elements of the motions, tendencies, and active powers, which are most universal in nature; and no small portion of natural science has been thus sketched out. We do not, however, deny that other instances can, perhaps, be added, and our divisions changed according to some more natural order of things, and also reduced to a less number; in which respect we do not allude to any abstract classification, as if one were to say, that "bodies desire the preservation, exaltation, propagation, or fruition of their nature;" or, that "motion tends to the preservation and benefit either of the universe, (as in the case of those of resistance and connection,) or of extensive wholes, (as in the case of those of the greater congregation, revolution, and abhorrence of motion,) or in particular forms, as in the case of the others. For, although such remarks be just, yet, unless they terminate in matter and construction, according to true definitions, they are speculative and of little use. In the mean time, our classification will suffice, and be of much use in the consideration of the predominance of powers, and examining the wrestling instances which constitute our present subject.
For, of the motions here laid down, some are quite invincible, some more powerful than others, which they confine, check, and modify; others extend to a greater distance, others are more immediate and swift, others strengthen, increase, and accelerate the rest.
The motion of resistance is most adamantine and invincible. We are yet in doubt whether such be the nature of that of connection; for we cannot with certainty determine whether there be a vacuum, either extensive or intermixed with matter. Of one thing, however, we are satisfied, that the reason assigned by Leucippus and De
mocritus for the introduction of a vacuum, | bound down, or otherwise confined, and yet strive (namely, that the same bodies could not other wise comprehend and fill greater and less spaces,) is false. For there is clearly a folding of matter, by which it wraps and unwraps itself in space within certain limits, without the intervention of a vacuum. Nor is there two thousand times more of vacuum in air than in gold, as there should be on this hypothesis; a fact demonstrated by the very powerful energies of fluids, (which would otherwise float like fine dust in vacuo,) and many other proofs. The other motions direct and are directed by each other according to their strength, quantity, excitement, emission, or the assistance or impediments they meet with.
For instance, some armed magnets hold and support iron of sixty times their own weight; so far does the motion of lesser congregation predominate over that of the greater; but if the weight be increased, it yields. A lever of a certain strength will raise a given weight, and so far the motion of liberty predominates over that of the greater congregation, but if the weight be greater, the former motion yields. A piece of leather stretched to a certain point does not break, and so far the motion of continuity predominates over that of tension, but if the tension be greater, the leather breaks, and the motion of continuity yields. A certain quantity of water flows through a chink, and so far the motion of greater congregation predominates over that of continuity, but if the chink be smaller, it yields. If a musket be charged with ball and powdered sulphur alone, and fire be applied, the ball is not discharged, in which case the motion of greater congregation overcomes that of matter, but when gunpowder is used, the motion of matter in the sulphur predominates, being assisted by that motion and the motion of avoidance in the nitre; and so of the rest. For wrestling instances (which show the predominance of powers, and in what manner and proportion they predominate and yield) must be searched for with active and industrious diligence.
The methods and nature of this yielding must also be diligently examined; as, for instance, whether the motions completely cease or exert themselves, but are constrained. For, in the bodies with which we are acquainted, there is no real, but an apparent rest, either in the whole or in parts. This apparent rest is occasioned either by equilibrium or the absolute predominance of motions. By equilibrium, as in the scales of the balance, which rest if the weights be equal. By predominance, as in perforated jars, in which the water rests, and is prevented from falling by the predominance of the motion of connection. It is, however, to be observed (as we have said before) how far the yielding motions exert themselves For, if a man be held stretched out on the ground against his will, with arms and legs
with all his power to get up, the struggle is not the less, although ineffectual. The real state of the case (namely, whether the yielding motion be, as it were, annihilated by the predominance, or there be rather a continued although an invisible effort) will perhaps appear in the concurrence of motions, although it escape our notice in their conflict. For instance, let an experiment be made with muskets; whether a musket ball, at its utmost range in a straight line, or, as it is commonly called, point blank, strike with less force when projected upwards, where the motion of the blow is simple, than when projected downwards, where the motion of gravity concurs with the blow.
The rules of such instances of predominance as occur, should be collected: such as the following; the more general the desired advantage is, the stronger will be the motion; the motion of connexion, for instance, which relates to the intercourse of the parts of the universe, is more powerful than that of gravity, which relates to the intercourse of dense bodies only. Again, the desire of a private good does not, in general, prevail against that of a public one, except where the quantities are small. Would that such were the case in civil matters!
49. In the twenty-fifth rank of prerogative instances, we will place suggesting instances; such as suggest or point out that which is advanta geous to mankind; for bare power and knowledge, in themselves, exalt, rather than enrich human nature. We must, therefore, select from the general store, such things as are most useful to mankind. We shall have a better opportunity of discussing these when we treat of the application to practice; besides, in the work of interpretation, we leave room, on every subject, for the human or optative chart; for it is a part of science to make judicious inquiries and wishes.
50. In the twenty-sixth rank of prerogative instances, we will place the generally useful instances. They are such as relate to various points, and frequently occur, sparing, by that means, considerable labour and new trials. The proper place for treating of instances and contrivances, will be that in which we speak of the application to practice, and the methods of experiment. All that has hitherto been ascertained, and made use of, will be described in the particular history of each art. At present, we will subjoin a few general examples of the instances in question.
Man acts, then, upon natural bodies (besides merely bringing them together or removing them) by seven principal methods: 1. By the exclusion of all that impedes and disturbs; 2. By compression, extension, agitation, and the like; 3. By heat and cold; 4. By detention in a suitable place; 5. By checking or directing motion; 6. By peculiar harmonies; 7. By a seasonable and