The laws of The most general of all phenomena is the curvilinear motion are motion of bodies in free space; it is observed through first applied the whole extent of the solar system.

to astrono

mical phe

nomena.

54 The application of this science to the arts of life.

tion,

55

The mechanical history of nature begins therefore with astronomy. Here, from the general phenomena of the planetary motions, is evinced the fact of the mutual deflection of every body towards every other body, and this in the inverse proportion of the squares of the distance, and the direct proportion of the quantity of matter. This is the fact of UNIVERSAL GRAVITATION, indicating the agency, and measuring the intensity, of the universal force of mutual gravity.

Having established this as an universal fact, the natural philosopher proceeds to point out all the particular facts which are comprehended under it, and whose peculiarities characterise the different movements of the solar system. That is, in the language of philosophy, he gives a theory or explanation of the subordinate phenomena; the elliptical motions of the planets and comets, their mutual disturbances; the lunar irregularities; the oblate figure of the planets; the nutation of the earth's axis; the precession of the equinoxes; and the phenomena of the tides and trade winds: and he concludes with the theory of the parabolic motion of bodies projected on the surface of this globe, and the motion of pendulums.

As he goes along, he takes notice of the applications which may be made to the arts of life of the various doctrines which are successively established; such as chronology, astronomical calculation, dialling, navigation, gunnery, and the measuring of time.

If a square parcel of sand be lying on the table, and The nature the finger be applied to any part of it to push it along of gravita- the table, that part is removed where will, but the you rest remains in its place; but if it is a piece of sand-stone of the same materials and shape, and the finger is applied as before, the whole is moved; the other parts accompany the part impelled by the finger in all its motions.

56 and of cobesion.

57

Mode of

From the moon's accompanying the earth in all its motions round the sun, we infer a moving force which connects the moon and earth. In like manner, we must conclude that a moving force connects the particles of the stone; for we give the name force to every thing which produces motion: We call it the force of COHESION; a term which, like gravitation, expresses merely a fact.

This seems to be the next phenomenon of the universe in point of extent.

Having, from the general phenomenon, established investiga- the existence of this force, the philosopher proceeds to ting the ascertain the laws by which its exertions are regulated; Jaws of co- which is the ascertaining its distinctive nature and properties. This he does in the same way that he ascertained the nature of planetary gravitation, viz. by observing more particularly the various phenomena.

hesion.

Here is opened a most extensive and varied field of observation, in which it must be acknowledged that very little regular and marked progress has been made. The variety of the phenomena, and the consequent variety in the nature of the connecting forces, appear as yet in4

conceivably great; and there seems little probability of Mechanicsi our being able to detect in them all any sameness, com- Philosophy, bined with the other distinguishing circumstances, as we have done in the case of gravity. Yet we should not despair. Boscovich has shown, in the most unexcep tionable manner, that although we shall suppose that every atom of matter is endued with a perfectly similar force, acting in a certain determined ratio of the small and imperceptible distances at which the particles of matter are arranged with respect to each other, the external or sensible appearances may, and must, have all that variety which we observe. He also shows very distinctly how, from the operation of this force, must arise some of the most general and important phenomena which characterise the different forms of tangible bodies.

We observe the chief varieties of the action of this CORPUSCULAR force on the bodies which we denominate hard, soft, solid, fluid, vaporous, brittle, ductile, elastic. We see instances where the parts of bodies avoid each other, and require external force to keep them together, or at certain small distances from each other. This is familiar in air, vapours, and all compressible and elastic bodies.

This is evidently a most curious and interesting subject of investigation. On the nature and action of these corpuscular forces depends the strength or firmness of solids, their elasticity, their power of communicating motion, the pressure, and motion, and impulse of fluids; nay, on the same actions depend all the chemical and physiological phenomena of expansion, fusion, congelation, vaporisation, condensation, solution, precipitation, absorption, secretion, fermentation, and animal and vegetable concoction and assimilation.

Out of this immense store of phenomena, this inexhaustible fund of employment for our powers of inves tigation, the natural philosopher selects those which lead directly to the production or modification of sensible motion.

He will therefore consider,

been

58

nature.

pro

1. The communication of motion among detached and The free bodies, establishing the laws of impulse or collision, duction of This has always been considered as the elementary doc-motion by trine of mechanical philosophy, and as the most familiar impulse bas fact observed in the material world; and in all ages thought the philosophers have been anxious to reduce all actions of most fanibodies on each other to impulse, and have never thought liar fact in a phenomenon completely explained or accounted for till it has been shown to be a case of impulse. This it is which has given rise to the hypotheses of vortices, ethers, magnetic and electric fluids, animal spirits, and a multitude of fancied intermediums between the sensible masses of matter, which are said in common language to act on each other. A heavy body is supposed to fall, because it is impelled by a stream of an invisible fluid moving according to certain conditions suited to the case. The filings of iron are supposed to be arranged round a magnet, by means of a stream of magnetic fluid issuing from one pole, circulating perpetually round the magnet, and entering at the other pole, in the same manner as we observe the flote-grass arranged by the current of a brook.

59

Mechani- logies between the phenomena of gravitation and cohecal Philo- sion, will be at least ready to entertain very different sophy. notions of this matter. He will be so far from think

60 Motion

from the

reaction.

ing that the production of motion by impulse is the most familiar fact in nature, that he will acknowledge it to be comparatively very rare; nay, there are some appearances in the facts, which are usually considered as instances of impulsion, which will lead him to doubt, and almost to deny, that there has ever been observed an instance of one body putting another in motion by coming into absolute contact with it, and striking it; and he will be disposed to think that the production of motion in this case is precisely similar to what we observe when we gently push one floating magnet towards another, with their similar poles fronting each other. There seems to be will be the same production of motion in the one and diproduced minution of it in the other, and the same uniform moequality of tion of the common centre of gravity: and, in this case action and of the magnets, he sees completely the necessity of a law of motion, which is not an axiom, but is observed through the whole of nature, and which receives no explanation from any hypothesis of an intervening fluid, but is even totally inconsistent with them. We "that every action of one body on another is accompanied by an equal and opposite action of that other on the first." This is usually called the equality of action and reaction: it is not intuitive, but it is universal; and it is a necessary consequence of the perfect similarity of the corpuscular forces of the same kinds of matter. This general fact, unaccountable on the hypothesis of impelling fluids, ' is considered in the planetary motions as the unequivocal indication of the sameness of that gravity which regulates them all. The rules of good reasoning should make us draw the same conclusion here, that the particles of tangible matter are connected by equal and mutual forces, which are the immediate causes of all their sensible ac

61

Of motion as it respects the theory of machines, &c.

62 MECHA

NICS.

The nature

mean,

tions, and that these forces, like gravitation, vary with every change of distance and situation.

The laws of collision and impulsion being now established, either as original facts or as consequences of the agency of equal and mutual forces which connect the particles of matter, the philosopher considers,

2. The production of motion by the intervention of solid bodies, where, by reason of the cohesion of matter, some of the motions are necessarily confined to certain determinate paths or directions. This is the case in all motions round fixed points or axes, or along planes or curves which are oblique to the action of the forces.

This part of the study contains the theory of ma chines, pointing out the principles on which their energy depends, and consequently furnishing maxims for their construction and improvement. But these observations do not complete the discussion of the mechanism of solid bodies: they are not only solid and inert, but they are also heavy; therefore the action of gravity must be combined with the consequences of solidity. This will lead to discussions about the centre of gravity, the theory and construction of arches and roofs, the principles of stability and equilibrium, the attitudes of animals, and many particulars of this kind.

63 3. The philosopher will now turn his attention to anand defini- other form, in which tangible matter exhibits many intion of flui- teresting phenomena, viz. FLUIDITY. The first thing to dity. be attended to here is, What is that particular form of

existence? What is the precise phenomenon which cha- Mechaniracterises fluidity? What is the definition of a fluid? cal PhiloThis is by no means an easy question, and considerable sophy. objections may be stated against any definition that has been given of it. Sir Isaac Newton says, that a fluid is a body whose particles yield to the smallest impression, and by so yielding are easily moved among themselves. It may be doubted whether this be sufficiently precise; what is meant by the smallest impression? and what is easily moving? Is there any precise degree of impression to which they do not yield; and do they oppose any resistance to motion? And a stronger objection may be made: It is not clear that a body so constituted will exhibit all the appearances which a body acknowledged to be fluid does really exhibit. Euler offers some very plausible reasons for doubting whether it will account for the horizontal surface, and the complete propagation of pressure through the fluid in every direction; and therefore prefers selecting this last phenomenon, the propagation of pressure quáqua versum, as the characteristic of fluidity, because a body having this constitution (on whatever circumstance it may depend) will have every other observed property of a fluid. But this definition is hardly simple or perspicuous enough; and we think that the objections against Newton's more simple and intelligible definition are not unanswerable. Boscovich dsfines a fluid to be, a body whose particles exert the same mutual forces in all directions; and shows, that such particles must be indifferent, as to any position, with respect to each other. If no external force act on them, they will remain in every position, and will have no tendency to arrange themselves in one position rather than another; differing in this respect from the particles of solid, or soft, or viscid bodies; which require some force to change their respective positions, and which recover these positions again when but gently disturbed. Heillustrates this distinction very beautifully, by comparing a parcel of balls thrown on quicksilver, and attracting each other, with a parcel of magnets in the same situation. The balls will stick together, but in any position; whereas the magnets will always affect a particular arrangement.

64

When the characteristic phenomenon of fluidity has Of the presbeen selected, the philosopher proceeds to combine this sure and equilibrium property with gravity, and establishes the doctrines of of fluids, or HYDROSTATICS, or of the pressure and equilibrium of hydrostaheavy fluids, the propagation of this pressure in every tics. direction; and demonstrates the horizontality of surface assumed by all perfect fluids.

These doctrines and principles enable us to determine several very interesting circumstances respecting the mutual pressure of solids and fluids on each other; the pressures exerted on the bottoms and sides of vessels; the support and whole mechanism of floating bodies, &c.

65

He then considers how fluids will move when their of the mo. equilibrium of pressure is destroyed; and establishes the tion of doctrines of HYDRAULICS, containing all the modifica fluids, or tions of this motion, arising from the form of the ves. hydraulics, sels, or from the intensity or direction of the pressure which occasions it. And this subject is completed by the consideration of the resistance which fluids oppose to the motion of solid bodies through them, and their impulse on bodies opposed to their action.

These are very important matters, being the foundations of many mechanical arts, and furnishing us with some of our most convenient and efficacious powers for impelling

The importance

ty of these

science.

pour.

It is evident, that on these doctrines depend the aad difficul-knowledge of the motions of rivers and of waves; the branches of buoyancy, equilibrium, and stability of ships; the motion of ships through the waters; the action of the winds on the sails; and the whole arts of marine construction and seamanship. 67 The nature There is another general form of tangible matter and defini- which exhibits very different phenomena, which are also tion of va- extremely interesting; we mean that of VAPOUR. A vapour is a fluid; and all the vapours that we know are heavy fluids: they are therefore subject to all the laws of pressure and impulse, which have been considered under the article HYDRODYNAMICS. But they are susceptible of great compression by the action of external forces, and expand again when these forces are removed. In consequence of this compression and expansion, the general phenomena of fluidity receive great and important modifications; and this class of fluids requires a particular consideration. As air is a familiar instance, this branch of mechanical philosophy has been called PNEUMATICS.

68 The doc

tics.

Under this head we consider the pressure of the attrine of air mosphere, and its effects, both on solid and fluid bodies. or pneuma. It produces the rise of waters or other fluids in pumps and syphons, and gives us the theory of their construction it explains many curious phenomena of nature, such as the motions in the atmosphere, and their connection with the pressure of the air, and its effect on the barometer or weather-glass. Air, when in motion, is called wind; and it may be employed to impel bodies. The theory of its action, and of its resistance to moving bodies, are therefore to be considered in this place.

69

Of the

quence.

But besides their motions of progression, &c. such as we observe in winds, compressible or elastic fluids are susceptible of what may be termed internal motion; a kind of undulation, where the contiguous parts are thrown into tremulous vibrations, in which they are alternately condensed and rarefied; and these undulations are propagated along the mass of elastic fluid, much in the same way in which we observe waves to spread on the surface of water. What makes this an interesting subject of consideration is, that these undulations are the more ordinary causes of sound. A trembling chord, or spring, or bell, agitates the air adjoining to it: these agitations are propagated along the air, and by its intervention agitate the organ of hearing. The mechanism of these undulations has been much studied, and furnishes a very beautiful theory of musical harmony.

The philosopher examines the law of compressibility compressi- of air and other elastic fluids; and thus gets the knowbility of ledge of the constitution of the atmosphere, and of the elastic Huids, and action of those fluids when employed to impel solid boits conse- dies. Gunpowder contains an immense quantity of permanently elastic air, which may be set at liberty by inflammation. When this is done at the bottom of a piece of ordnance, it will impel a ball along the barrel, and discharge it from the muzzle, in the same way that an arrow is impelled by a bow. And thus having discovered in what degree this air presses in proportion to its expansion, we discover its action on the ball through the whole

2

length of the piece, and the velocity which it will fi- Mechani nally communicate to it. Here then is contained a cal e theory of artillery and of mines.

sophy.

70

elastic

Chemistry teaches us, that most bodies can be converted by fire into elastic fluids, which can be employed of the conto act on other bodies in the way of pressure or impulse, version of Thus they come under the review of the mechanical phi- bodies into losopher; and they have become interesting by being emfluids by. ployed as moving forces in some very powerful machines. re These discussions will nearly exhaust all the general mechanical phenomena. There remain some which are much more limited, but furnish very curious and important subjects of investigation.

71

or magn

tism.

The phenomena exhibited between loadstones or mag-Of the phenets and iron have long attracted attention; and the use nomena of to which the polarity of the loadstone has been applied, loadstone, namely, the directing the course of a ship through the pathless ocean, has rendered these phenomena extremely interesting. They are specified by the term MAGNETISM. Considerable progress has been made in the arrangement and generalization of them; but we have by no means been able hitherto to bring them all under one simple fact. The attention has been too much turned to the discovery of the ultimate cause of magnetism; whereas we should have rather employed our ingenuity in discovering all the general laws, in the same manner as Kepler and Newton did with respect to the celestial phenomena, without troubling themselves with the cause of gravitation. Dr Gilbert of Colchester was the first who considered the magnetical phenomena in the truly philosophical manner; and his treatise De Magnete may be considered as the first and one of the most perfect specimens of the Baconian or inductive logic. It is indeed an excellent performance; and when we consider its date, 1580, it is a wonder. Epinus's Tentamen Theorią Magnetismi is a most valuable work, and contains all the knowledge which we have as yet of the subject.

72

There is another class of mechanical phenomena which of electrihave a considerable affinity with the magnetical; we cal pheno mean the phenomena called ELECTRICAL. Certain bo- mena. dies, when rubbed or otherwise treated, attract and repel other bodies, and occasion a great variety of sensible motions in the neighbouring bodies. Philosophers have paid much attention to these appearances of late years, and established many general laws concerning them. But we have not been more successful in bringing them all under one fact, and thus establishing a complete theory of them, than in the case of magnetism. Franklin and

pinus are the authors who have been most successful in this respect. Dr Franklin in particular has acquired great celebrity by his most sagacious comparison of the phenomena; which has enabled him to establish a few general laws, almost as precise as those of Kepler, and of equally extensive influence. His discovery too of the identity of thunder and electricity has given an importance and dignity to the whole subject.

74

vision.

75

doubted whether light is corporeal.

76

as a part of

Mechani- sense of seeing form another class, which have always cal Philo been considered as making a branch of natural philososophy. phy in all seminaries of learning. It does not, however, obviously appear, that they are mechanical pheThe intimate nature of light is still a secret. Of the phenomena. nomena of Fortunately it is not necessary to be known to give us a very perfect theory of the chief phenomena. The general laws of optics are so few, so simple, and so precise, that our theories are perhaps more perfect here than in any other branch of physics; but these theories are as yet far removed from the rank of primary facts. Many unknown events happen before the phenomenon comes under the hands of the ordinary optician, so as to become the subjects of the simple laws of reflection and It has been refraction. It may even be doubted, and has been doubted, whether the phenomena of optics are cases of body in motion; whether all the lines which the optician draws are any thing but the directions along which certain qualities are exerted. The side of a ball which is next the candle may be bright and the other side dark, just as the side of a ball which is next the electrical globe is minus and the other side plus; and all this without any intervening medium. Apparition or visibility may be a quality of a body, depending on the proximity and position of another body, without any thing between them, just as weight is; and this quality may be cognizable by our faculty of seeing alone, just as the pressure of a heavy body is by our feeling alone. How optics The first thing which made it probable that mechanicame to be cal philosophy had any thing to do with the phenomena considered of optics, was the discovery of Mr Roemer," that apmechanical parition was not instantaneous;" that some time elapsed philosophy, between the illumination of a body and its being seen at a distance. He discovered, that it was not till 40 minutes after the sun illuminated one of Jupiter's satellites that it was seen by the inhabitants of this globe. If therefore a sun were just created, it would be 40 minutes before Jupiter would be illuminated by him, and 200 before the Georgian planet would be illuminated. Here The nature then is motion. It is therefore highly probable that of light is there is something moved; but it is still doubted whether this something, which we call LIGHT, is a matter emitted from the shining body, and moving with great velocity, and acting on and affected by other bodies, in the various phenomena of optics, or whether it is acertain state of a medium which is thus propagated, as we see that waves are propagated along the surface of water, or sonorous undulations through the mass of air, while the water or air itself is hardly moved out of its place. Either of these suppositions makes optics a legitimate branch of mechanical philosophy; and it is the philosopher's business to examine both by the received laws of motion, and se which of them gives consequences which tally with the phenomena. This has been done; and we imagine that a complete incompatibility has been demonstrated between the consequences of the undulations of an elastic medium, and the phenomena of optics; while the consequences of the other or vulgar notion on this subject are perfectly consistent with mechanical laws. There are some things in this hypothesis very far beyond our power to conceive distinctly; but they are all similar in this respect to many facts acknowledged by all; and there is no phenomenon that is inconsistent with the legitimate consequences of the hypothesis. This gives it great probability; and this probability is confirmed by

77

still undetermined.

crease of

Such is the field of observation to the mechanical phi- The prolosopher of the present day. We may hope to extend bable init, and by degrees apply its doctrines even to the unseen the above motions which take place in chemistry and phisiology. extensive But we must, in the first place, perfect our knowledge field of oband description of the sensible motions and actions of servation. bodies. Those of fluids still demand much investigation; and till these are thoroughly understood, it is not time to attempt penetrating further into the recesses of nature.

In the prosecution of this study, it is found that every Investiga

tion of the

change which can be observed in the state of a body, law that with respect to motion by the action of another body, is action is accompanied by an equal and opposite change in the always state of that other body. Thus, in the phenomena of equal and gravitation, it is observed that the deflections of the sun opposite to and planets are mutual. The same thing is observed in reaction. the actions of magnets on each other and on iron; it is also observed in the attractions and repulsions of electrical bodies; and it also obtains in all the phenomena of impulse and of corporeal pressure. It is therefore an universal law of motion, that action is always equal and opposite to reaction: but this must be considered merely as a matter of fact, a contingent law of nature, like that of gravitation. The contrary is perfectly conceivable, and involves no contradiction. That this is so, is evident. from the proceedings of philosophers, who in every new case make it their business to discover by experiment whether this law was observed or not. It was among the last discoveries made by Sir Isaac Newton in bis examination of the celestial motions. This being the case, it should never be assumed as a principle of reasoning till its operation has been ascertained by observation. 8r It has been owing to this improper procedure that much The term false reasoning has been introduced into mechanical phi- occasioned losophy, and particularly into the theory of impulsion or much the communication of motion by impulse. In consider- wrangling ing this subject, a term has been introduced which has and misconoccasioned much wrangling and misconception; we mean ception on the term INERTIA. It serves indeed to abbreviate language, but it has often misled the judgment. When used with cautious attention to every circumstance, it expresses nothing but the necessity of a cause to the production of any effect: but it is generally used as expressing a quality inherent in matter, by which it resists any change of state, or by which it maintains its present state. Matter is said to be inert; and as every thing which changes the motion of a body is called a force, and as this inertia of A is supposed to change the motion of B, it is called vis inertiæ ; and yet matter is said to be indifferent as to motion or rest, and to be inactive. These

are

inertia has

this sub

"ject.

.

sophy.

The vulgar say that B repels A; so say the dynamists, MechaniThe abettors of invisible fluids say, that a stream of fluid cal Philoissuing from B impels A in the opposite direction. All naturalists agree in saying, that an active force connected with B has destroyed the motion of A, and consider this curious phenomenon as the indication and characteristic of a discovery. The same inference is made from the motion produced in B: it is considered by all as effected by a force exerted or occasioned by the presence of A; and the dynamists and the vulgar say that A repels B. And both parties conclude, from the equal changes made on both bodies, that the changing forces are equal; here acknowledging, that they observe an equality of action and reaction; and they add this to the other instances of the extent of this law of motion.

Mechani- are surely very incongruous expressions. This obscure cal chilo- discourse has arisen from the poverty of all languages, sophy. which are deficient in original terms, and therefore employ figurative ones. Force, action, resistance, are all appropriated terms related to our own exertions; and some resemblance between the external effects of these exertions and the effects of the connecting qualities of natural bodies, has made us use them in our disquisitions on these subjects. And as we are conscious that, in order to prevent our being pushed by another from our place, we must resist, exerting force; and that our resistance is the reason why this other man has not accomplished his purpose, we say, that the quiescent body resists being put in motion, and that its inertia is discovered by the diminution made in the motion of the impelling body and upon the authority of this vis inertia as a first principle, the phenomena of impulsion are explained, and the law of equal action and reaction is established.

82

Its proper

But all this procedure is in contradiction to the rules of inductive logic; and the obscurity and confusion which has arisen from this original misconception, the consequent incongruity of language, and the awkward attempts that have been made to botch and accommodate it to the real state of things, have occasioned a dispute, and the only dispute, in natural philosophy which has not yet been settled, and never can be settled, while such misconceptions are allowed to remain.

If the word inertia be taken as expressing not a qua meaning, lity of matter, but a law of human judgment respectwith an ex-ing matter, as expressing our necessity of inferring the ample. agency of a moving force whenever we observe a change of motion, all difficulties will vanish, and the equality of action and reaction will be inferred, as it should be, from the phenomena of collision. There will be inferred a vis insita corpori impellenti, not quâ moventi, but quá corpori; and this inference will carry us through all the mysteries of corporeal action, as it conducted Sir Isaac Newton in his grand researches.

A

B

D

Let us just consider how we reason in a new case. Let A and B be two magnets fastened on the ends of two long wooden laths AE, BF, which turn horizontally on pivots C, D, like compass needles, with their north poles fronting each other, 12 inches apart; and let A be pushed towards B, SO that it would move uniformly with the C velocity of two inches in a second. The phenomena which have been observed are as follow: A will gradually diminish its velocity; and when it has advanced about nine inches, will stop completely. B, in the mean time will gradually acquire motion; and E when it has advanced about nine inches, will have a velocity of about two inches per second, with which it will continue to move uniformly. Now what is inferred from these phenomena? Because the motion of A is gradually retarded, we infer that a retarding force, that is, a force in the direction BA, has acted on it. And since this would not have happened if B had not been there, and always happens when B is there, we infer that B is either its cause or the occasion of its action.

F

All this while no one thinks of the inertia or inactivity of B, but, on the contrary, conclude this to be a curious instance of its activity; and most people conclude that both bodies carry about with them a vis insita both when at rest and when in motion.

$3

actual con

84

If other phenomena give unquestionable evidence It is doubtthat in ordinary collisions, there is the same changes ful whether of motion, produced without mathematical contact, the tact has same inferences must be drawn ; and a scrupulous natu- ever been ralist will doubt whether contact should make any change observed. in our reasonings on the subject, and whether actual contact ever has been or can be observed. He will also be convinced, that while this is the general, or perhaps universal, process of nature in producing motion by impulse, all explanations of the action of bodies è distanti, The folly by the intervention of ethers and other invisible fluids, of suppoare nothing but multiplying the difficulties; for in place sing interof one fact, the approach of one magnet (for instance) vening to another, they substitute millions of unseen impulses, ethers, &e. each of which equally needs an explanation. And if this fluid be supposed to produce its effects by any peculiarity in its constitution, as in the case of Newton's elastic ether proposed by him to explain gravitation, the hypothesis substitutes, in the most unqualified manner, millions of similar phenomena for the one to be explained; for there is the same want of a second fluid in order to produce that mutual recess of the particles of the ether which constitutes its elasticity.

85

other bodies

And this seems to be the limit to our inquiries into The quality all the classes of natural phenomena. We find the mas- of bodies ses or the particles of matter endued in fact with quali- whereby ties which affect the state of other particles or masses, at they affect smaller or at greater distances from each other according is inseruto certain general rules or laws. This ultimate step in table by us. the constitution of things is inscrutable by us. It is arrogance in the highest degree for us to say, that because we do not comprehend how there is inherent in a body any quality by which another body may be affected at any distance from it, therefore no such quality is possible. It is no less so to say, that matter has no active property but that of moving other matter by impulse; and that because it may be so moved, and also by the agency of our own minds, therefore, when it is not moved by impulse, it is moved by minds. The same almighty FIAT which brought a particle of matter into existence could bring those qualities equally into existence; and the how in both is equally beyond our comprehension.

86

But, on the other hand, we must guard against the This should incurious resting on this consideration as a stop to fur- not, howther inquiry. There may be species of matter posses- further in

ever, stop

sed quiries.