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below its surface, and affecting the needle in its eye sees better if the coject be moved a litile polarity, it must act at a great distance.

farther, and not nearer. Again, it is certain, that Again, if there be any magnetic force, which in projectiles the impact is not so violent at too acts by sympathy between the globe of the earth short a distance as a little afterwards.* Such are and heavy bodies, or between that of the moon the observations to be made on the measure of and the waters of the sea, (as seems most proba- motions as regards distance. ble from the particular floods and ebbs which There is another measure of motion in space occur twice in the month,) or between the starry which must not be passed over, not relating to sphere and the planets, by which they are sum- progressive, but spherical motion : that is, the moned and raised to their apogees; these must expansion of bodies into a greater, or their conall operate at very great distances.* Again, traction into a lesser sphere. For, in our measure some conflagrations and the kindling of flames of this motion, we must inquire what degree of take at very considerable distances, with particu- compression or extension bodies easily and readily lar substances, as they report of the naphtha of | admit of, according to their nature, and at what Babylon. Heat, too, insinuates itself at wide point they begin to resist it, so as, at last, to bear Jistances, as does also cold, so that the masses it no farther; as, when an inflated bladder is comof ice which are broken off and float upon the pressed, it allows a certain compression of the Northern Ocean, and are borne through the At- air, but, if this be increased, the air does not suflantic to the coast of Canada, become perceptible fer it, and the bladder is burst. by the inhabitants, and strike them with cold We have proved this by a more delicate expefrom a distance. Perfumes also (though here riment. We took a metal bell, of a light and there appears to be always some corporeal emis- thin sort, such as is used for salt-cellars, and imsion) act at remarkable distances; as is experi- merged it in a basin of water, so as to carry the cnced by persons sailing by the coast of Florida, air contained in its interior down with it to the or parts of Spain, where there are whole woods bottom of the basin. We had first, however, of lemons, oranges, and other odoriferous plants, placed a small globe at the bottom of the basin, or rosemary and marjorum bushes, and the like. over which we placed the bell. The result was, Lastly, the rays of light and the impression of that if the globe were small, compared with the sound act at extensive distances.

interior of the bell, the air would contract itself, Yet all these powers, whether acting at a small and be compressed without being forced out, but, or great distance, certainly act within definite if it were too large for the air readily to yield to distances, which are well ascertained by nature: it, the latter became impatient of the pressure, so that there is a limit depending either on the raised the bell parıly up, and ascended in bubmass or quantity of the bodies, the vigour or

bles. faintness of the powers, or the favourable or im- To prove, also, the extension (as well as the peding nature of the medium, all of which compression) which air admits of, we adopted the should be taken into account and observed. We following method. We took a glass egg, with a must also note the boundaries of violent motions, small hole at one end; we drew out the air by such as missiles, projectiles, wheels, and the violent suction at this hole, and then closed the like, since they are also manifestly confined to hole with the finger, immersed the egg in water, certain limits.

and then removed the finger. The air being conSome motions and virtues are to be found of a strained by the effort made in suction, and dilated directly contrary nature to these, which act in beyond its natural state, and, therefore, striving contact, but not at a distance ; namely, such as to recover and contract itself, (so that if the egg operate at a distance, and not in contact, and had not been immersed in water, it would have again act with less force at a less distance, and drawn in the air with a hissing sound,) now drew the reverse. Sight, for instance, is not easily in a sufficient quantity of water to allow the air effective in contact, but requires a medium and to recover its former dimensions.t distance; although I remember having heard from It is well ascertained, that rare bodies (such as a person, deserving of credit, that in being cured air) admit of considerable contraction, as has of a cataract, (which was done by putting a small been before observed ; but tangible bodies (such silver needle within the first coat of the eye, to as water) admit of it much less readily, and to a remove the thin pellicle of the cataract, and force less extent. We investigated the latter point by it into a corner of the eye,) he had distinctly seen the following experiment. the needle moving across the pupil. Still, though

We had a leaden globe made, capable of conthis may be true, it is clear that large bodies can- taining about two pints, wine measure, and of not be seen well or distinctly, unless at the vertex tolerable thickness, so as to support considerable of a cone, where the rays from the object meet at soine distance from the eye. In old persons, the

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pressure. We poured water into it through an In the explosion of several cannon at once, aperture, which we afterwards closed with melted (which are sometimes heard at the distance of lead, as soon as the globe was filled with water, thirty miles,) the sound of those nearest to the so that the whole became perfectly solid. We spot, is heard before that of the most distant. next flattened the two opposite sides with a heavy Even in sight, (whose action is most rapid,) it is hammer, which necessarily caused the water to clear that a definite time is necessary for its exoccupy a less space, since the sphere is the solid ertion, which is proved by certain objects being of greatest content; and when hammering failed, invisible from the velocity of their motion, such from the resistance of the water, we inade use of as a musket ball. For the flight of a ball is 100 a millor press, till at last the water, refusing to swist to allow an impression of its figure to be submit to a greater pressure, exuded, like a fine conveyed to the sight. dew, through the solid lead. We then computed This last instance, and others of a like nature, t'ie extent to which the original space had been have sometimes excited in us a most marvellous reduced, and concluded that water admitted such doubt, no less than whether the image of the sky a ilgree of compression when constrained by and stars is perceived as at the actual moment of great violence.

its existence, or rather a little after, and whether The more solid, dry, or compact bodies, such there is not (with regard to the visible appearance as stones, wood, and metals, admit of much less, of the heavenly bodies) a true and apparent time, and, indeed, scarcely any perceptible compression, as well as a true and apparent place, which is or expansion, but escape by breaking, slipping observed by astronomers in parallaxes.* forward, or other efforts; as appears in bending peared so incredible to us, that the images or wood, or steel for watch-springs, in projectiles, radiations of heavenly bodies could suddenly be hammering, and many other motions, all of which, conveyed through such immense spaces to the together with their degrees, are to be observed sight, and it seemed that they ought rather to be and examined in the investigation of nature, transmitted in a definite time. That doubt, howeither to a certainty, or by estimation, or compari- ever, (as far as regards any great difference beson, as opportunity permits.

tween the true and apparent time,) was subse46. In the twenty-second rank of prerogative quently completely set at rest, when we consider instances, we will place the instances of the the infinite loss and diminution of size as regards course, which we were also wont to call water the real and apparent magnitude of a star, cccainstances; borrowing our expression from the sioned by its distance, and at the same time ob. water hour-glass, employed by the ancients in- served at how great a distance (at least sixty stead of those with sand. They are such as miles) bodies which are merely white can be measure nature by the moments of time, as the suddenly seen by us. For there is no doubt, that last instances do by the degrees of space. For the light of heavenly bodies not only far surpass all motion or natural action takes place in time, the vivid appearance of white, but even the light more or less rapidly, but still in determined mo- of any flame (with which we are acquainted) in ments, well ascertained by nature. Even those the vigour of its radiation. The immense velocity actions which appear to take effect suddenly, and of the bodies themselves, which is perceived in in the twinkling of an eye, (as we express it,) are their diurnal motion, and has so astonished thinkfound to admit of greater or less rapidity. ing men, that they have been more ready to believe

In the first place, then, we see that the return in the motion of the earth, renders the motion of of the heavenly bodies to the same place, takes radiation from them (marvellous as it is in its place in regular times, as does the flood and ebb rapidity) more worthy of belief. That which has of the sea. The descent of heavy bodies towards weighed most with us, however, is, that if there the earth, and the ascent of light bodies towards were any considerable interval of time between the heavenly sphere, take place in definite times, the reality and the appearance, the images would according to the nature of the body, and of the often be interrupted and confused by clouds medium through which it moves. The sailing formed in the mean time, and similar disturbances of ships, the motions of animals, the transmission of the medium. Let this suffice with regard 10 of projectiles, all take place in times, the sums the simple measures of time. of which can be computed. With regard to heat, It is not merely the absolute, but still more the we see that boys in winter bathe their hands in relative measure of motions and actions which the flame without being burned; and conjurors, by must be inquired into, for this latter is of great quick and regular movements, overturn vessels use and application. We perceive that the flame filled with wine or water, and replace them with- of fire-arms is seen sooner than the sound is heard, out spilling the liquid, with several similar in- although the ball must have struck the air before stances. The compression, expansion, and erup- the flame, which was behind it, could escape: the tion of several bodies, takes place more or less reason of which is, that light moves with greater rapidly, according to the nature of the body, and

This is a singular approximation to Romer's discovery of its motion, but still in definite moments.

time being required for the propagation of light. Vol. 111.-52

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velocity than sound. We perceive, also, that vi- | not altogether remaiņed there for more than one sible images are received by the sight with greater hour and a half, there remains a most pleasing rapidity than they are dismissed, and for this rea- perfume, not inferior to the flower itself, for a son, a violin string touched with the finger appears whole year. It must be observed, however, that double or triple, because the new image is received the perfume does not acquire its full strength, till before the former one is dismissed. Hence, also, about a month after the infusion. In the distillarings when spinning, appear globular, and a lighted tion of aromatic plants macerated in spirits of torch, borne rapidly along at night, appears to have wine, it is well known that an aqueous and useless a tail. Upon the principle of the inequality of phlegm rises first, then water containing more of motion, also, Galileo attempted an explanation of the spirit, and lastly, water containing more of the the flood and ebb of the sea, supposing the earth aroma; and many observations of the like kind, to move rapidly, and the water slowly, by which well worthy of notice, are to be made in distillameans the water, after accumulatiny, would at tions. But let these suffice as examples. intervals fall back, as is shown in a vessel of 47. In the twenty-third rank of prerogative inwater made to move rapidly. He has, however, stances, we will place instances of quantity, imagined this on data which cannot be granted, which we are also wont to call the doses of na. (namely, the earth’s motion,) and, besides, does ture, (borrowing a word from medicine.) They not satisfactorily account for the tide taking place are such as measure the powers by the quantity every six hours.

of bodies, and point out the effect of the quantity An example of our present point, (the relative in the degree of power. And, in the first place, measure of motion,) and, at the same time, of its some powers only subsist in the universal quanremarkable use of which we have spoken, is con- tity, or such as bears a relation to the conformaspicuous in mines filled with gunpowder, where tion and fabric of the universe. Thus the earth immense weights of earth, buildings, and the like, is fixed, its parts fall. The waters in the sea flow are overthrown and prostrated by a small quantity and ebb, but not in the rivers, except by the adof powder; the reason of which is decidedly this, mission of the sea. Then, again, almost all parthat the motion of the expansion of the gunpowder ticular powers act according to the greater or less is much more rapid than that of gravity, which quantity of the body. Large masses of water would resist it, so that the former has terminated are not easily rendered foul, small are. New before the latter has commenced. Hence, also, in wine and beer become ripe and drinkable in small missiles, a strong blow will not carry them so far skins, much more readily than in large casks. If as a sharp and rapid one. Nor could a small por- an herb be placed in a considerable quantity of tion of animal spirit in animals, especially in such liquid, infusion takes place rather than impregnavast bodies as those of the whale and elephant, tion, if in less, the reverse. A bath, therefore, have ever bent or directed such a mass of body, and a light sprinkling, produce different effects on were it not owing to the velocity of the former, the human body. Light dew, again, never falls, and the slowness of the latter in resisting its but is dissipated and incorporated with the air; inotion.

thus we see that in breathing on gems the slight In short, this point is one of the principal foun- quantity of moisture, like a small cloud in the air, dations of the magic experiments, (of which we is immediately dissolved. Again, a piece of the shall presently speak,) where a small mass of same magnet does not attract so much iron as the matter overcomes and regulates a much larger, if whole magnet did. There are some powers where there be but an anticipation of motion, by the the smallness of the quantity is of more avail; velocity of one before the other is prepared to act. as in boring, a sharp point pierces more readily

Finally, the point of the first and last should be than a blunt one; the diamond, when pointed, observed in all natural actions. Thus, in an infu- makes an impression on glass, and the like. sion of rhubarb, the purgative property is first Here, too, we must not rest contented with a extracted, and then the astringent; we have ex. vague result, but inquire into the exact proportion perienced something of the same kind in steeping of quantity requisite for a particular exertion of violets in vinegar, which first extracts the sweet power. For one would be apt to suppose that the and delicate odour of the flower, and then the power bears an exact proportion to the quantity; more earthy part, which disturbs the perfume; so that if a leaden bullet of one ounce, for instance, that if the violets be steeped a whole day, a much would fall in a given time, one of two ounces sainter perfume 18 extracted than if they were ought to fall twice as rapidly, which is most erresteeped for a quarter of an hour only, and then neous. Nor does the same ratio prevail in every taken out; and since the odoriferous spirit in the kind of power, their difference being considerable. violet is not alıundant, let other and fresh violets The measure, therefore, must be determined by be steeped in the vinegar everv quarter of an hour, experiment, and not by probability or conjecture. us many as six times, when the infusion becomes Lastly, we must in all our investigations of 50 strengthened, that although the violets have I nature observe what quantity, or dose, of the body

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is requisite for a given effect, and must at the or some such matter, and forcing in a piece of same time be guarded against estimating it at too some pulpy root, or the like, at each end; then inuch or too little.

they force the root or other pellet with a ramrod 18. In the twenty-fourth rank of prerogative to the opposite end, from which the lower pellet instances, we will place wrestling instances, is emitted and projected with a report, and that which we are also wont to call instances of pre- before it is touched by the other piece of root of dominance. They are such as point out the pre- pellet, or by the ramrod. We have examples of dominance and submission of powers compared their escape from tension, in the motion of the with each other, and which of them is the more air that remains in glass eggs after suction, in energetic and superior, or more weak and inferior. strings, leather, and cloth, which recoil after tenFor the motions and effects of bodies are com- sion, unless it be long continued. The schools pounded, decomposed, and combined, no less define this by the term of motion " from the form than the bodies themselves. We will exhibit, of the element;" injudiciously enough, since this therefore, the principal kinds of motions or active motion is to be found not only in air, water, or powers, in order that their comparative strength, fire, but in every species of solid, as wood, iron, and thence a demonstration and definition of the lead, cloth, parchment, &c., each of which has instances in question, may be rendered more clear. its own proper size, and is with difficulty stretched

Let the first motion be that of the resistance of to any other. Since, however, this motion of matter, which exists in every particle, and com- liberty is the most obvious of all, and to be seen pletely prevents its annihilation ; so that no con- in an infinite number of cases, it will be as well flagration, weight, pressure, violence, or length to distinguish it correctly and clearly; for some of time. can reduce even the smallest portion of most carelessly confound this with the two others matter to nothing, or prevent it from being some of resistance and connection ; namely, the freething, and occupying some space, and delivering dom from pressure with the former, and that from itself, (whatever straits it be put to,) by changing tension with the latter ; as if bodies when comits form or place, or, if that be impossible, re- pressed yielded or expanded to prevent a penemaining as it is, nor can it ever happen that it tration of dimensions, and, when stretched, should either be nothing or nowhere. This mo- rebounded and contracted themselves to prevent tion is designated by the schools (which generally a vacuum. But if the air, when compressed, name and define every thing by its effects and in- could be brought to the density of water, or wood conveniences, rather than by its inherent cause) to that of stone, there would be no need of any by the axiom, " that two bodies cannot exist in penetration of dimensions, and yet the compresthe same place,” or they call it a motion, “ to pre. sion would be much greater than they actually vent the penetration of dimensions.” It is use- admit of. So, if water could be expanded till it less to give examples of this motion, since it exists became as rare as air, or stone as rare as wood, in every body.

there would be no need of a vacuum, and yet the Let the second motion be that which we term expansion would be much greater than they acthe motion of connexion, by which bodies do not tually admit of. We do not, therefore, arrive at allow themselves to be separated at any point from a penetration of dimensions or a vacuum, before the contact of another body, delighting, as it the extremes of condensation and rarefaction, were, in the mutual connexion and contact. This whilst the motion we speak of stops and exerts is called by the schools a motion “to prevent a itself much within them, and is nothing more vacuum.” It takes place when water is drawn than a desire of bodies to preserve their specific up by suction or a syringe, the flesh by cupping, density, (or, if it be preferred, their form,) and or when the water remains without escaping from not to desert them suddenly, but only to change perforated jars, unless the mouth be opened to by degrees, and of their own accord. It is, admit the air, and innumerable instances of a however, much more necessary to intimate to

mankind (because many other points depend Let the third be that which we term the motion upon this) that the violent motion which we call of liberty ; by which bodies strive to deliver mechanical, and Democritus (who, in explaining themselves from any unnatural pressure or ten- his primary motions, is to be ranked even below sion, and to restore themselves to the dimensions the middling class of philosophers) termed the suited to their mass; and of which, also, there motion of a blow, is nothing else than this motion are innumerable examples. Thus, we have ex- of liberty, namely, a tendency to relaxation from amples of their escaping from pressure, in the compression. For, in all simple impulsion or water in swimming, in the air in flying, in the flight through the air, the body is not displaced water again in rowing, and in the air in the un. or moved in space, until its parts are placed in dulations of the winds, and in the springs of an unnatural state, and compressed by the impelwatches. An exact instance of the motion of ling force. When that takes place, the different compressed air is seen in children's popguns, 'parts urging the other in succession, the whole is which they make by scooping out elder branches, , moved, and that with a rotatory as well as pre

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gressive motion, in order that the parts may, by Let the sixth be that which we term the motion this means, also, set themselves at liberty, or of acquisition, or the motion of need. It is that by inore readily submit. Let this suffice for the which bodies placed amongst others of a heteromotion in question.

genous and, as it were, hostile nature, if they meet Let the fourth be that which we term the mo- with the means or opportunity of avoiding them tinn of matter, and which is opposed to the last. and uniting themselves with others of a more For, in the motion of liberty, bodies abhor, reject, analagous nature, even when these latter are not and avoid a new size or volume, or any new ex- closely allied to them, immediately seize and, as pansion or contraction, (for these different terms it were, select thieni, and appear to consider it as have the same meaning,) and strive, with all their something acquired, (whence wederive the name.) power, to rebound and resume their former density. and to have need of these latter bodies. For in. On the contrary, in the motion of matter they are stance, gold, or any other metal in leaf, does not anxious to acquire a new volume or dimension, like the neighbourhood of air; jf, therefore, they and attempt it willingly and rapidly, and occa- meet with any tangible and thick substance, (such sionally by a most vigorous effort, as in the ex- as the finger, paper, or the like,) they immediately ample of gunpowder. The most powerful, or, at adhere to it, and are not easily torn from it. least, most frequent, though not the only instru- Paper, too, and cloth, and the like, do not agree ments of this motion, are heat and cold. For with the air, which is inherent and mixed in their instance, the air, if expanded by tension, (as by pores. They readily, therefore, imbibe water or suction in the glass egg,) struggles anxiously to other liquids, and get rid of the air. Sugar, or a restore itself; but if heat be applied, it strives, sponge, dipped in water or wine, and though part on the contrary, to dilate itself, and longs for a of it be out of the water or wine, and at some larger volume, regularly passing and migrating height above it, will yet gradually absorb them. into it, as into a new form, (as it is termed :) nor, Hence, an excellent rule is derived for the after a certain degree of expansion, is it anxious opening and dissolution of bodies. For, (not to to return, unless it be invited to do so by the ap- mention corrosive and strong waters, which force plication of cold, which is not indeed a return, their way,) if a body can be found which is more but a fresh change. So, also, water, when con- adapted, suited, and friendly to a given solid, fined by compression, resists, and wishes to be than that with which it is by some necessity come as it was before, namely, more expanded ; united, the given solid immediately opens and but if there happen an intense and continued dissolves itself to receive the former, and excludes cold, it changes itself readily and of its own ac- or removes the latter.* Nor is the effect or power cord, into the condensed state of ice; and if the of this motion confined to contact, for the electric cold be long continued, without any intervening energy (of which Gilbert and others after him warmth, (as in grottos and deep caves,) it is have told so many fables) is only the energy changed into crystal or similar matter, and never excited in a body by gentle friction, and which resumes its form.

does not endure the air, but prefers some tangible Let the fifth be that which we term the motion substance, if there be any at hand. of continuity. We do not understand by this, sim- Let the seventh be that which we term the mople and primary continuity with any other body, tion of greater congregation, by which bodies are (for that is the motion of connexion,) but the con-borne towards masses of a similar nature, for intinuity of a particular body in itself. For it is stance, heavy bodies towards the earth, light to most certain, that all bodies abhor a solution of the sphere of heaven. The schools termed this continuity, some more and some less, but all par- natural motion, by a superficial consideration of tially. In hard bodies, (such as steel and glass,) it, because produced by no external visible agent, the resistance to an interruption of continuity is which made them consider it innate in the sub most powerful and efficacious, whilst, although in stances; or, perhaps, because it does not cease, liquids it appears to be faint and languid, yet it is which is little to be wondered at, since heaven not altogether null, but exists in the lowest degree, and earth are always present, whilst the causes and shows itself in many experiments, such as and sources of many other motions are sometimes bubbles, the round form of drops, in thin threads absent, and sometimes present. They, therefore, which drip from roofs, the cohesion of glutinous called this perpetual and proper, because it is substances, and the like. It is most conspicu- never interrupted, but instantly takes place when ous, however, if an attempt be made to push this the others are interrupted, and they called the separation to still smaller particles. Thus, in others adscititious. The former, however, is in mortars, the pestle produces no effect after a cer- reality weak and slow, since it yields, and is tain degree of contusion, water does not penetrate inferior to the others as long as they act, unless small fissures, and the air itself, notwithstanding the mass of the body be great; and although this ils subtilty, does not penetrate the pores of solid motion have so filled men's minds, as almost to vessels at once, but only by long continued in

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