its proper effect (surprising as the saying may appear) consistency, not fluidity. This is also very well seen in the instance of snow, where, though the substance be a concrete of air and water, and the water and air be separate fluids, yet the union of the two produces consistency. Should any one object, that this consistency may be occasioned by the condensation of the aqueous part by cold, and not by means of the incorporated air, he will correct himself by observing that froth also, which is a body similar to snow, is not in any way condensed by cold. Yet, if he still press the objection, by saying that in the formation of foam there is still an antecedent condensation, not indeed by the action of cold, but by agitation and concussion: let him take a lesson from the boys, who with a slight inspiration of itself int globules, the diameter of which is ported by sound reason, but almost repugnant to considerably greater than the filament previously it. For that other of which they speak, has for formed. In the same way we see that the water with difficulty admits of being broken into more minute particles, since it does not, without having been shaken, exude by its natural gravity through pertures and crevices, if they be somewhat minute. It is evident, then, that there is a tendency to continuity in fluids also, but weak. On the contrary, however, it is strong in solids, and predominates over the natural motion, or that of gravity. For if any one conceives that in a pillar of wood or stone, the upper parts do not throughout affect descent, but rather to maintain themselves in entirely the same position, he will easily set himself right, by considering that a column or a similar structure, if the altitude is disproportioned to the base, or exceeds the due relation to it, cannot stand, but is precipitated by its own gravity. So that in very elevated piles | air through a pipe or reed, and by the aid of some of building it is necessary to make them incline water rendered rather more viscid by mixing a to the pyramidal form, and narrow to an apex. little soap with it, form a strange turriform conWhat that principle in nature is, however, which geries of bubbles. determines the intensity or weakness of the affection of continuity, will not easily occur to the inquirer. It might, perhaps, be suggested that the parts of solids are more concentrated and compact, those of liquids more lax, or that in liquids there was an ether, the principle of fluidity, which was wanting in solids and the like. But neither of these explanations is reconcileable to truth; for it is apparent that snow and wax, which can be divided, cast into form, and receive the impression of other bodies, are a much rarer substance than melted quicksilver or lead; as is proved by a comparison of their weight. But if any one still insists that it is possible that snow or wax, though (as a whole) less gross than quicksilver, may, nevertheless, have its parts disposed more closely and compactly, yet, that as it is a porous body, containing many cavities and much air, it is, therefore, rendered lighter as a whole as is the case of pumicestone, which, though in comparing the size of both, it be perhaps lighter than wood, nevertheless, if both be Of the Harmony of sentient Bodies with insentient. ground to a dust, the dust of the pumicestone will outweigh that of the wood, because the porosity of the former no longer continues: these are well observed and well objected facts. But what shall be said of melted snow or wax, where the same interstices are now filled up: or what of gum mastic and the like substances, which have no perceptible cavities of the kind, and are yet lighter than several liquids? As to the allegation of an ether by the virtue and impulse of which things are put into the state of being fluid, that, no doubt, is at the first glance probable, and falls in kindly with the common notions: but in the experience of actual nature, it is much more hard to admit, and inaccurate, being not merely unsup The case, in fact, stands thus: bodies at the contact of a friendly or homogeneous body relax and fall to solution; at that of a dissimilar body they contract and hold themselves erect and aloof. The application, therefore, of an incongruous body is the cause of consistency. Thus we see oil mixed with water, as takes place in preparing unguents, in so far divest itself of the fluidity which before prevailed, both in the water and the oil. On the contrary, we observe paper moistened with water become flaccid and lose its consistency, (which was considerable, by reason of the air which had penetrated its pores,) but when moistened with oil, the cohesion is less affected, because it has less congruity with paper. We see the same thing take place also in sugar and the like substances, which soften into commixture with water and wine; and not only blend intimately with these fluids, but even attact and suck them up. VII. The affections of bodies endowed with sense and destitute of it, have great conformity with one another, except that in the sentient body, there is the addition of spirit. For the pupil of the eye corresponds with a mirror and with water, and by a similar property admits and refracts the images of light and of visible objects. The organ, too, of hearing is analogous to the obstructed part of a cave-like passage, from which part the voice and all sound best reverberates. The attractions, also, of inanimate objects, and again their affections of horror and flight, (those I mean which come of their own spontaneous motion,) are correlative to smell and to odours grateful and offensive in the case of animals. But the capacity of touch and taste, like a prophet and interpreter, delivers to the mind all the modes either of forcible appeal, or of benign and insinuating flattery to the sense, which are incident to inanimate substances, and all the forms they assume under the influence of these affections. For compressions, expansions, corrosions, separations, and the like, are, in things without life, invisible in their progress, and are not perceived till the effect is manifest. But all violence to the organization of animals is accompanied with a sense of pain, according to their different kinds and peculiar natures, owing to that sentient essence which pervades their frames. And from this principle may be inferred the knowledge whether haply any animal possesses some additional sense, besides those commonly observed, and what senses and how many can possibly exist in the whole circle of animated nature. For from the affections of matter duly analyzed, will follow the number of the senses, if there be only the sufficing organs for the operation of such senses, and the presence of spirit to inform them. Of violent Motion, that it is the rapid Motion and Discursation of the Particles of a Body, in consequence of Pressure, but perfectly invisible. VIII. Violent motion, (as it is termed,) by which missiles, as stones, arrows, cannon balls, and the like, move through the air, is of all descriptions of motion nearly the most familiar. And we may note here, the singular and supine indifference which men have discovered in observing and investigating this kind of motion. Nor is a faulty way of tracing the nature and power of it attended with only trivial loss; since it is of unlimited use, and as it were the life and informing principle of projectiles, engines, and all the applications of mechanical power. Yet many conceive that they have completely acquitted themselves of their part in the investigation, if they but pronounce such motion to be violent, and contradistinguish it from natural. And no doubt it is the system of Aristotle and his school, to instruct men what to say, not what to think; to teach a man by what devices of affirming or denying, he may get clear of a disputant in argument, not how, by force of thought, he may get clear of a difficulty in the conviction of his own mind. Others, rather more attentive, laying hold of the position that two bodies cannot exist in one place, say that it follows as a consequence that the stronger body propel, and the weaker be dislodged: that this dislodging or flight, if a less force is used, continues no longer than the duration of the original impulse, as in protrusion; but if a greater, the impulsion continues for a time, even after the removal of the impelling body, till it gradually slackens, as in throwing. And here, again, according to another inveterate habit of the same school, they catch only at the commencement of the thing, indifferent to its progression and termination, and drag in all that follows under the head of the beginning; whence, with an overweening haste and impatience, they break off their train of thought in the midst. For in what they say of bodies giving way at the impelling force, there is something; but why the motion should continue after the urging body is withdrawn, and consequently the necessary alternative of the weaker and stronger body mingling is at an end, of this they say nothing, not sufficiently apprehending the scope of their own observations. Others, however, more attentive and steady in investigating, having marked the force of the air in winds and the like instances, which is capable of throwing down trees and towers, have supposed that the force which urges and accompanies projectiles, after the first impulsion, ought to be referred to the air accumulating and rushing in behind the body in motion, by the impulse of which that body is borne along, like a ship in the expanse of water. And such persons, at least, do its conclusion; yet they, nevertheless, do not not quit their subject, but carry their thought to attain to the truth. The cause in reality is this. The principal motion seems to be in the parts of the volant body itself, which parts being imperceptible to vision, on account of their extreme tenuity, escape the notice of men, not sufficiently attentive to their subject, and passing it over with a cursory glance. But to one who gives it a sounder examination, it is clearly evident, tha. the harder bodies are, they are the more impatient of pressure, the more acutely sensitive to it, as it were; so much so, that if disturbed ever so little from their natural position, they endeavour with great velocity of movement to free themselves from its effect, and resume their original state. To effect which, the several parts, beginning with the part struck, successively propel one another, in the same way as an external force, and keep up that motion vigorously; hence results a continuous and, though invisible, intense vibration of the parts. And this we see exemplified in glass, sugar, and similar brittle substances, which, it they be divided by a blade or edged instrument, are, as it were, in a moment broken down in other parts distant from the line described by the blade. Which evidently proves that the motion of pressure travels to the parts of these substances successively. This motion pervading all the parts of the body, and trying, as it were, their compactness, causes the breaking down of that part, where, from the structure, the cohesion is weak. Yet does not this motion, though it agitates and hitherto investigated only in part, and that part comparatively unimportant. IX. The theory of fire-arms-of a motion so powerful and so remarkable, is imperfect, and, in the more important part, defective. For it is said in explanation that the gunpowder, after having been converted into flame and volatilized, expands and occupies more space; whence it follows, that as two bodies cannot exist in the same space, otherwise a jumbling of their dimensions would ensue, or the elementary form be destroyed, or a preternatural arrangement of the internal parts of the body be the effect, (for this is what they say,) that the impeding body is ejected or broken. And what they say contains something. For this tendency is both an affection of matter, and an ingredient in the motion itself. Yet they err in this, that in their over hasty way of determining, they dilatation of a body, and do not accurately consider what comes first in the order of nature. For that the substance of the gunpowder, after having been converted into flame, must occupy a larger space, is doubtless a thing of necessity; but that the substance of the gunpowder should be inflamed at permeates the whole, come into view, till a visible of the cause of Motion in Fire-arms, which has been break or divulsion of continuity takes place. Again, we observe, if we happen to bend and compress between the thumb and forefinger the two ends of a wire, or bit of cane, or the harder part of a pen, (or similar bodies which unite flexibility with a certain degree of elasticity,) they anon spring from the hand. The cause of which motion is evidently discernible not to be in the extremities compressed by the fingers, but in the middle part, which is the seat of forcible pressure, to relieve itself from which, the motion comes into play. And in this instance it is clearly shown, that the alleged cause of motion, the impulsion of the air, is inadmissible. For here there is no concussion to let in a rush of air. This is also proved by a slight experiment, when we press the fresh and smooth ball of a plum, drawing the fingers gradually together, and in this manner let it go. For in that instance also compression is substituted for percussion. But the most conspicuous effect of this interior motion is in the revo-jump at once to the necessary consequence of the lutions and gyrations of missiles while flying. The missiles, indeed, proceed onwards, but they make their progression in spiral lines, that is, by straight-lined and rotatory motion together, and indeed this curvilinear motion is so fleet, and at the same time so easy, and somehow so familiar to things, as to excite a doubt in my mind whe-all, and that so instantaneously, is not determined ther it does not depend on some higher principle. Yet I think that the cause of this fact is no other than the same we are now handling. For the concussion of the body occasions an excessive impetus in all its parts and particles, to effect in some way or other their extrication and freedom. The body, therefore, not only acts and flies forth in a straight line, but strives to move from every point in it at once, and, therefore, whirls round; for in both ways it somewhat relieves itself of its impuise. Now this, which in the harder solids is a somewhat recondite and latent property, is in the softer ones evident, and, so to speak, palpable. For as wax, and lead, and similar soft bodies, when struck with a mallet, give way not only in the line of percussion, but laterally every way; so, in like manner, hard or resisting bodies move in a straight line and periphery at once. For the retrocession of soft bodies in their substance, and of hard ones in their place, is the same in its principle, as is evidently seen in the structure of the soft body, and in the affection of the hard one, exhibited in its flight and volant path. Meantime let none think that besides this motion, (which is the cardinal point,) I do not ascribe a certain degree of effect to the conveyance of the air, which is capable of assisting, obstructing, modifying, and regulating the principal motion; for its power is far from being inconsiderable. And this doctrine of violent or mechanical motion (which has been hitherto unknown) is, as it were, the fountain-head of practical mechanics. by a like necessity, but depends on an antagonism, and comparative force of motions. For there is not a doubt, that the compact and heavy body which is expelled or dislodged by this motion, offers considerable resistance before it gives way, and, if it happen to be the stronger, is victorious; that is to say, the flame, in that case, does not cast out the ball, but the ball stifles the flame. If, therefore, instead of gunpowder, you take sulphur, asphaltum, or the like, bodies which are also quickly inflammable, and (as the closeness of particles in bodies hinders ignition) reduce them to a grain like gunpowder, mixing up with it a small quantity of the ashes of the juniper, or some other very combustible wood; yet, should the nitre be wanting, that rapid and powerful motion does not follow the motion to perfect inflammation is impeded and fettered by the resisting body, so that it cannot fully expand and take effect. For, besides the motion of inflammation, which chiefly arises from the sulphureous part of the gunpowder, there is yet another powerful and violent motion in the case. This is caused by the crude watery ether, which is extricated from the nitre in part, but chiefly from the charcoal, and which not only itself dilates, as exhaled essences are wont to do, on the application of heat, but at the same time (which is the principal circumstance) by a motion of extreme rapidity, flies off and breaks forth from the heat and flame, thus distending and opening passages for the inflam mation to follow. Of this motion we see the simplest form in the crackling of the dry leaves of laurel or ivy, when we cast them into the fire, and still more in salt, which approximates more nearly to the substance under examination. We also often observe something like this in the tallow of candles when melted, and in the windy rustle of green wood set on fire. But it is chiefly discernible in quicksilver, which is an extremely crude substance, not unlike the water of a chalybeate spring; and the force of it, if tried by the application of fire, and prevented from egress, not greatly inferior to that of gunpowder itself. Men ought, therefore, to be admonished and conjured from this example, not in their investigation of causes to catch at only one element, and so too lightly to pronounce upon them; but to look around them with caution, and rivet their contemplation more intensely and profoundly. such a prodigious interval, what operations, movements, and changes presented themselves on the face of the globe, in engines, plants, animals, and so on, which on account of their distance would not equal the bulk of the minutest straw. Now, in bodies of such immense bulk and magnitude, that by the vastness of their dimensions they can overcome the greatness of distance, and come into visibility; it is evident from certain comets, that changes take place as they move in the expanse of the heavens. I allude to those comets, which have retained a certain unvaried relation of position to the fixed stars, such as that which in our own day appeared in Cassiopea. But as respects the earth, after having penetrated into the interior recesses of it, leaving that crust and mixture of substances which composes its surface and contiguous parts, there seems to exist there also an eternal immobility, analogous to that supposed to Of the dissimilarity of things celestial and subluna-be found in heaven. For it is beyond a doubt, ry, in regard to eternity and mutability, that it that if the earth underwent changes at an extreme has not been proved to be true. depth beneath its surface, the influence of such changes, even in the region we tread, would produce greater calamities than any we behold. Most X. The received opinion that the universe is regu-earthquakes, certainly, and volcanic eruptions, do Iarly divided and discriminated by spheres, as it were, and that there is one system of heavenly and another of sublunary being, appears to have been adopted, not without rational grounds, provided the opinion is applied with proper modifications. For there is no doubt that the regions situated beneath the lunar orb, and above it, differ in many and important respects. Yet is not that belief more certain than this other, that the bodies in both spheres have tendencies, appetencies, and motions which are common to both. We ought then to imitate the unity of nature, to discriminate those spheres rather than rend them asunder, and not break down the continuity of our contemplation. But with respect to another received opinion, that the heavenly bodies undergo no change, but that the terrestrial or elementary (as they are called) are subject to change; and that the matter of the last resembles a courtezan ever seeking the embracement of new bodies, but of the other a matron linked to one in stable and inviolable union; it seems but a popular notion, weak, and originating in appearances and superstition. This notion appears to be tottering, and without foundation, when viewed in either way. For neither does their imagined eternity consist with heaven, nor their mutability with earth. For, with respect to heaven, we cannot rest upon it as a reason for changes not happening there, that they do not emerge to our view, the view of man being prevented no less by distance of place than by tenuity of bodies. For various changes are found to take place in the air, as is evident in heat, cold, smells, sounds, which do not fall within the line of sight. Nor, again, I suppose, would the eye, if placed in the orb of the moon, desery across not rise from a great but a very moderate depth, since they affect such an inconsiderable part of the surface. For in proportion as such visitations agitate a wider area of the earth's surface, in the same proportion we are to suppose that their bases and primitive seats enter deeper into the bowels of the earth. These earthquakes, therefore, which are greater, (in the extent of surface agitated I mean, not in violence of tremefaction,) and which but rarely happen, may be assimilated to comets of the description we have mentioned, which are also unusual. So that the proposition with which we set out remains unshaken, namely, that between heaven and earth there is no great difference as respects stability and change. But if any one is influenced to a different opinion by the regularity and seeming exactness of the motion of the heavenly bodies, we have before us the ocean, the solitary handmaid as it were of eternity, which exhibits no less unchangeable uniformity than they. Lastly, if any one shall still insist, that nevertheless it cannot be denied, but that on the surface of the globe, and the part contiguous to it, changes innumerable take place, but that in heaven it is not so, we would have him thus answered; that we do not carry the parallel through every part; and yet if we take the upper and middle regions of air (as they are termed) for a surface and exterior integument of heaven, just as among us we regard that space over which are distributed animals, plants, minerals, as a surface or outer integument of earth, we behold in both manifold reproductions and vicissitudes, in full operation. It would, therefore, seem that all the disorder, contention, and commotion of the universe, has its seat on the frontiers of heaven and earth alone. As in civil society, it often happens in the ordinary course of | ness in heaven," it is also said that "generations things, that the borders of two adjacent kingdoms pass away, but the earth abideth for ever." And are wasted with a perpetual succession of inroads and affrays, while the interior provinces of either kingdom enjoy continued and profound tranquillity. And none who bestows a proper attention on the subject will make an objection of religion. For it was only a heathen flourish to ascribe to a material heaven the quality of being impregnable to decay. The sacred Scriptures ascribe eternity and destructibility equally to heaven and earth, though they assign to them a different glory and an unequal reverence. For if it be recorded, that "the sun and moon bear faithful and eternal wit that both are transitory is a doctrine contained in the same oracle of God, namely, that "heaven and earth shall pass away, but the word of the Lord will not pass away.” These things we have noted, not from any ambition of novelty in opinion, but because, not in ignorant conjecture, but instructed by examples, we foresee that these fantastical divorces, and distinctions of objects and of regions, beyond what truth admits, will prove a serious impediment to true philosophy and the contemplation of nature. W. G. G. THE THEORY OF THE FIRMAMENT. BUT as so many foiling inconveniences are found to spring up on all sides, it should be deemed satisfactory if any thing can be avouched less revolting. But bodies that are simple and perfect, not of such as Let us, therefore, construct a scheme of the universe, according to that measure of history hitherto known to us, reserving for our future judgment all new lights, after history, and through history, our philosophy, by induction, may have reached a maturer age. But we will, in the out-cury and sulphur, and generally crude and fat set, premise some points that have reference to the matter composing the heavenly bodies, whence their motion and formation may be better understood; afterwards setting forth our thoughts and ideas of that motion itself, the chief subject under discussion. Nature, then, in the separating of matter, seems to have drawn an impassable bar between the rare and dense, and to have assigned the globe of the earth to the order of the dense; but every thing, from the very surface of the earth, and its waters, to the utmost extremity of the firmament, to that of the rare or volatile, as it were, to twin classes of first principles, not indeed of equal but of suitable portions. Nor indeed does either the water clinging to the clouds, or the wind pent up in the earth, disarrange this natural and appropriate position of things: but this difference, between rare or volatile, and dense or tangible, is entirely primordial or essential, and is what the system of the universe chiefly has recourse to. It proceeds from a state of things the most simple possible this is from the abundance and scarceness of matter, in proportion to its extension. What belong to the order of subtile or volatile, as found here among us, (we are speaking of those bodies, or, in other words, bodies that have a turous through many casualties tries.' |