Principles of natural philosophy, or, A new theory of physics : founded on gravitation, and applied in explaining the general properties of matter, the phenomena of chemistry, electricity, galvanism, magnetism, & electro-magnetism

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Introduction

THE office of natural philosophy is^ to enquiie into the phenomena of material beings^ and to ascertain their causes.

Experiments and observations form tlie true basis of philosophy : by these we becooie ai;«- quainted with the phenomena^ and axe directed to the powers or causes, which produce them ; and having discovered these^ we frequently observe^ that they are the results of more general causes ; which^ being themselves discovered^ become principles in the explication^ not only of those phe^ nomena by means of which they are determined, but also of all others to which they are. a^iUca-. ble; and when they are found adeqiiate to this purpose^ the principles themselves are •estabHshed.

To assist our enquires of this nature. Sir /. Newton has furnished the following excellent rules^ at the commencement of the ibird Book of the Principia.

IV DEDICATION.

ness of a family connection with you, I have experienced your unremitted friendship and kindness, and have reaped great advantage from your advice and encouragement.

For these and similar reasons, I dedicate to you this Volume, the result of much labour and thought ; and am solicitous that you would accept of it as a small tribute of my gratitude and respect.

THOMAS EXLEY.

BusTOL, March Ui, 1829.

INTRODUCTION.

THE office of natural philosophy is, to enquire into the phenomena of material beings, and to ascertain their causes.

Experiments an<l observations form the true basis of philosophy : by these we become acquainted with the phenomena, and are directed to the powers or causes, which produce them ; and having discovered these, we frequently observe, that they are the results of more general causes; which, being themselves discovered, become principles in the explication, not only of those phenomena by means of which they are determined, but also of all others to which they are applicable; and when they are found adequate to this purpose, the principles themselves are established.

To assist our enquires of this nature. Sir /. Newtoyi has furnished tlie following excellent rules, at the commencement of the third Book of the Principia,

IV DEDICATION.

ness of a family connection with you, I have experienced your unremitted friendship and kindness, and have reaped great advantage from your advice and encouragement.

For these and similar reasons, I dedicate to you this Volume, the result of much labour and thought ; and am solicitous that you would accept of it as a small tribute of my gratitude and respect.

THOMAS

Bristol, Mwch Ul, 1829.

INTRODUCTION.

THE office of natural philosophy is^ to enquiie into the phenomena of material beings^ and to ascertain their causes.

Experiments and observations form tbe true basis of philosophy : by these we becooie acquainted with the phenomena^ and axe directed to the powers or causes, which produce them ; and having discovered these^ we frequently observe^ that they are the results of more general causes ; which^ being themselves discovered^ become principles in the explication^ not only of those phenomena by means of which they are determined, but also of all others to which they are applicable; and when they are found adequate to this purpose, the principles themselves are f^tabHshed.

To assist our enquires of this nature. Sir /. Newton has furnished the following excellent rules, at the commencement of the third Book of the Principia.

IV DEDICATION.

ness of a family connection with you, I have experienced your unremitted friendship and kindness, and have reaped great advantage from your advice and encouragement.

For these and similar reasons, I dedicate to you this Volume, the result of much labour and thought ; and am solicitous that you would accept of it as a small tribute of my gratitude and respect.

THOMAS EXLEY.

BusTOL, Karck Ui, 1829.

INTRODUCTION.

THE office of natural philosophy is, to enquire into the phenomena of material beings, and to ascertain their causes.

Experiments and observations form th« true basis of philosophy : by these we become acquainted with the phenomena, and are directed to the powers or causes, which produce them ; and having discovered these, we frequently observe, that they are the results of more general causes ; which, being themselves discovered, become principles in the explication, not only of those phenomena by means of which they are determined, but also of all others to which they are appHcable; and when they are found adequate to this purpose, the principles themselves are established.

To assist our enquires of this nature. Sir /. Naalon has furnished the following excellent rules, at the commencement of the third Book of the Principia.

Vi INTRODUCTION.

Rule I. ''We are to admit no more causes 6t natural things^ than such as are both true^ and sufficient to explain their appearances."

Rule II. '' Therefore, to the same natural effects we must, as far as possible, assign the same causes.'^

Rule III. '' The qualities of bodies, which admit neither intension nor remission of degrees, and which are found to belong to all bodies withih the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever.'*

Rule IV. '' In experimental philosophy we are to look upon propositions collected by general' induction from phenomena, as accurately or very nearly true, notwithstanding any contrary hypotheses that maybe imagined, till such time as other phenomena occur, by which they may eilher be made more accuratie, or liable to exceptions.'' (See Motte'g Trari. vol. ii. p. 203.)

Matter, which in its various states and forms, is thesubjec^t 6f natural philosophy, is perc^eptible to man by means of its powers, actih^ on ihe senses, which evidently, in infinite wisdom^ are adapted to rfeceiye the impressions of these powers : powers which theM^^hrJes ai^e in continual operation, and appear to constitute the Wry ' essence of matter; fof,' from thesei all lis blfier universal properties as &r as they are discovered, maybe derived, while those properties themselves, cannot result the one from any bther of those which are

INTRODUCTION. VII

known ; neither can the less general properties be derived from any of them, or from each other.

These powers are denominated attraction and Impulsion. Their nature is not known, but the laws of their operation have been at least partially developed : that both these belong to matter is incontrovertible : did attraction exist without repulsion, matter would be conglomerated into one bodyj and if there were repulsion only, all bodies would be universally dispersed, supposing tliem io consist of separate particles.

Universal experience and careful observation, shew, that bodies at rest have a tendency to remain at rest, and those which are in motion to continue that motion uniformly in a straight line ; were there no tendency of this kind, there would be no such changes in the state of bodies as we observe, and the resistance, which bodies are known to oppose to forces or powers applied, could not exist.

Not only when bodies are acted on in opposition to gravity, or their descent towards the earth, is this resistance experienced, but even in that very direction, for any force, applied to make a descending body move more swiftly downward, is resisted in proportion to its quantity, and the same is true in every other case.

But we find, that the great and distant bodies of the solar system are continually deflected from the line of their direction, into curves concave towards the sun, which is included within their

Vi INTRODUCTION.

Rule I. ''We are to admit no more causes 6t natural things^ than such as are both true^ and sufficient to explain their appearances."

Rule IL '' Therefore, to the same natural effects we must, as far as possible, assign the same causes."^

Rule III. '' The qualities of bodies, which admit neither intension nor remission of degrees, and which are found to belong to all bodies withih the reach of our experiments, are to be esteemed the universal qualities of all bodies whatsoever/*

Rul£ IV. '' In experimental philosophy we are to look upon propositions collected by general iriddction from phenomena, as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.'' (See Motte'g Trah. vol. ii. p. 203.)

Matter, which in its various states and forms, is the subject of natural philosophy, is perc^eptible to man by means of its powers, acting oiitlie senses, which evidently, in infinite wisdom^ aire JQidapted to rtceive the itnpressions of these powers : powers which theni^ehrJes are in continual operatioh, and appear to constitute the^ very ' essence of maitter ; foi*,' from these) all '' its other universal properties as &r as they are discovered, 'maybe derived, while those properties themselves, cannot result the one from aby other of those which are

INTRODUCTION. VII

known ; neither cau the less general properties be derived from any of them, or from each other.

These powers are denominated attraction and i-epu1sion. Their nature is not known, but the laws of their operation have been at least partially developed : that both these belong to matter is incontrovertible : did attraction exist without repulsion, matter would be conglomerated into one body^ and if there were repulsion only, all bodies would be universally dispersed, supposing them to consist of separate particles.

Universal experience and careful observation, shevr, that bodies at rest have a tendency to remain at rest, and those which are in motion to continue that motion uniformly in a straight line ; were there no tendency of this kind, there would be no such changes in the state of bodies as we observe, and the resistance, which bodies are known to oppose to forces or powers apphed, could not exist.

Not only when bodies are acted on in opposition to gravity, or their descent towards the earth, is this resistance experienced, but even in that very direction, for any force, applied to make a. descending body move more swiftly downward, is resisted in proportion to its quantity, and the same is true in every other case.

But we find, that the great and distant bodies of the solar system are continually deflected from the line of their direction, into curves concave towards the sun, which is included within their

J.

VJU INTRODUCTION.

orbits^ and situated in the planes of those orbits : hence they are attracted or acted upon by some force directed towards that quarter ; in a similar manner are the secondary planets urged towards their primaries^ and observation shews^ that all these bodies tend towards each other ; hence they disturb each other's motions^ producing several apparent irregularities. And we find also that the attractions of the moon^ of the sun^ and by consequence^ eyen those of the planets^ disturb the equilibrium of the waters of our globe^ and cause the ebbings and Sowings of the ocean and their variations.

Also^ all the parts of the earth are held together by the principle of attraction ; since^ were it not for this force^ the motion of the globe on its axis would disperse its parts^ and the least effort applied^ would crumble the hardest bodies to powder^ if indeed^ we could suppose the existence of hard bodies.

Every one must have observed, that the parts of bodies tend to each other, because it is continually apparent, from the globular figure, which small portions of liquids, as water, oil, mercury, &c., assume; and from the ready union of two or more small drops into one larger drop ; and this shews, that not only those atoms, which are contiguous, act on each other, but likewise that a similar action continually operates between those particles, which are on the opposite sides of the drop.

INTRODUCTION. IX

The same is shewn by the ascent of water in line glass tubes, on the sides of vessels, into the interstices of sand, ashes, and other porous bodies, as also by its absorption by sugar, spunge, salt, &c. ; and again, we see that when melted metals, wax, resins, sulphur, &c., are cooled, their parts unite and form solid masses, and the same happens to water, and even to mercury, when at a sufficiently diminished temperature.

Thousands of instances presenting the univereality of such action between bodies and their parts, might be adduced from the phenomena of chemistry, electricity, magnetism, &c. ; shewing that the principle of attraction pervades the natural world, and is found wherever matter is found.

How near to tlie centers of the atoms of matter this force of attraction extends from all sides of that center, has not been ascertained ; but at distances very near tite center, an opposing force, called repulsion, has been observed, which force prevents tlie perfect coincidence of those centers, and consequently of the parts of bodies.

Nor, is the power of repulsion less universal, than that of attraction ; in no other way can we account for the easy motions of the parts of fluid bodies, one amongst another, whether liquids or gases : and it is to be noticed, that the various solid bodies are capable of the liquid form.

The parts of all bodies may be brought nearer toy;elher by the application of force ; bodies con-

VIII INTRODUCTION.

orbits^ and situated in the planes of those orbits : hence they are attracted or acted upon by some force directed towards that quarter ; in a similar manner are the secondary planets urged towards their primaries^ and observation shews^ that all these bodies tend towards each other ; hence they disturb each other's motions^ producing several apparent irregularities. And we find also that the attractions of the moon^ of the sun^ and by consequence^ even those of the planets, disturb the equilibrium of the waters of our globe, and cause the ebbings and Sowings of the ocean and their variations.

Also, all the parts of the earth are held together by the principle of attraction ; since, were it not for this force, the motion of the globe on its axis would disperse its parts, and the least effort applied^ would crumble the hardest bodies to powder, if indeed, we could suppose the existence of hard bodies.

Every one must have observed, that the parts of bodies tend to each other, because it is continually apparent^ from the globular figure, which small portions of liquids, as water, oil, mercury, &c., assume ; and from the ready union of two or more small drops into one larger drop ; and this shews, that not only those atoms, which are contiguous, act on each other, but likewise that a similar action continually operates between those particles, which are on the opposite sides of the drop.

INTRODUCTION. IX

The same is shewn by the ascent of water in fine glass tubes, on the sides of vessels, into the interstices of sand, ashes, and other porous bodies^ as also by its absorption by sugar, spunge, salt^ &c. ; and again, we see that when melted metals, wax, resins, sulphur, &c., are cooled, their parts unite and form solid masses, and the same hap^ pens to water, and even to mercury; when at a sufficiently diminished temperature.

Thousands of instances presenting the univef' sality of such action between bodies and their parts, might be adduced from the phenomena of chemistry, electricity, magnetism, &c. ; shewing that the principle of attraction pervades the natural world, and is found wherever matter is found.

How near to the centers of the atoms of matter this force of attraction extends from all sides of that center, has not been ascertained ; but at distances very hear the center, an opposing force^ called repulsion, has been observed, which force prevents the perfect coincidence of those centers, and consequently of the parts of bodies.

Nor, is the power of repulsion less universal, than that of attraction ; in no other way can we account for the easy motions of the parts of fluid bodies, one amongst another^ whether liquids or gases : and it is to be noticed, that the various solid bodies are capable of the liquid form.

The parts of all bodies may be brought nearer together by the application of force ; bodies con-

Viii INTRODUCTION.

orbits^ and situated in the planes of those orbits : hence they are attracted or acted upon by some force directed towards that quarter ; in a similar manner are the secondary planets urged towards their primaries^ and observation shews^ that all these bodies tend towards each other ; hence they disturb each other's motions^ producing several apparent irregularities. And we find also that the attractions of the moon^ of the sun^ and by consequence^ even those of the planets^ disturb the equilibrium of the waters of our globe^ and cause the ebbings and flowings of the ocean and their variations.

Also, all the parts of the earth are held together by the principle of attraction ; since, were it not for this force, the motion of the globe on its aus would disperse its parts, and the least effort applied^ would crumble the hardest bodies to powder, if indeed, we could suppose the existence of hard bodies.

Every one must have observed, that the parts of bodies tend to each other, because it is continually apparent, from the globular figure, which small portions of liquids, as water, oil, mercury, &c., assume ; and from the ready union of two or more small drops into one larger drop ; and this shews, that not only those atoms, which are contiguous, act on each other, but likewise that a similar action continually operates between those particles, which are on the opposite sides of the drop.

INTRODUCTION.

The same is shewn by the ascent of water in fine glass tubes, on the sides of vessels, into the interstices of sand, ashes, and other porous bodies, as also by its absorption by sugar, spunge, salt^ &c. ; and again, we see that when melted metals, wax, resins, sulphur, &c., are cooledj their parts unite and form solid masses, and the same bappens to water, and even to mercury, when at a sufficiently diminished temperature.

Thousands of instances presenting the universality of such action between bodies and their parts, might be adduced from the phenomena of chemistry, electricity, magnetism, &c. ; shewing that the principle of attraction pervades the natural world, and is found wherever matter is found.

How near to the centers of the atoms of matter this force of attraction extends from all sides of that center, has not been ascertained ; but at distances very near the center, an opposing force, called repulsion, has been observed, which force prevents the perfect coincidence of tliose centers, and consequently of the parls of bodies.

Nor, is the power of repulsion less universal, than (hat of nltraction ; in no other way can we account for the easy motions of the parts of fluid bodies, one amongst another, whether liquids or gases : and it is to be noticed, that the various solid bodies are capable of liie liquid form.

The parls of ail bodies may be brr)ught nearer together by the application of force ; bodies con-

X, INTRODUCTION.

tract by cold^ ,and expand by heat^ which indicates r^ej^ulsion ; the compressioq^ and subsequent ex« pan^ipn of elastic bodies shew the same^, and no bodies are fpund ^altogether void of elasticity. If a convex lens be placed on a plane surface of glass, its weight -is not sufficient to, bring the surfaces ii4Q contact, nor can this be perfectly effected by .ai|y forqe we afe able to apply ; besides which, \fe ha,Y|9 innumerable instances of this repulsiye force, Ja ey^y depa^rtment of the material world ; destitute of,4hi8> not a single atom of matter has. ever bef(ii £(^ufxd.or exhibiti^d; and,, although^ some pbenoiii- ^a , may possibly appear to be accounted for, iar di^pi^ndently of repulsion, as belonging to every atom of matter; .yet the expliqations rest on feigned hypptheses^ : and no phenomenon of nature contra- 4lic;ts tbe supposition that: this , principle is as uni- ^Dffrsal as matter itself . Therefore, by the rules, of SQund philosophy, we must adn^it the universal in* fluence of both attractipn and repulsion.

The attraction, which takes place between the distant bodies of the universe, (and which is clearly aspertained, to be^ the same ^b that power eaUed gravitation, by which bodies despepd towards the earth,) varies^ in. intensity,^ directly as, the quantity of m^^r, and reciprocally as the J^qus^re of the distance of the attracting bodies. < Sir Isaac Newton has left no doubt on this, subject. See the Principia, and Cotes' excellent Preface ; and, also^ consult the Authors who have since written on

INTRODUCTION.

physical astronomy, where it will be found that the truth of these laws is fully established. But the illustrious Newton and others, Iiave concluded that the attraction, by which the particles or atoms of bodies adhere together, observes a different law, and decreases at a greater rate. The 83th prop. Book i. of the Principia, is intended to prove this, for which purpose the 70th and 74th propositions are employed.

It should, however, be carefully observed, that the hypothesis of this beautiful theorem requires the attractive forces to be directed to every point of the sphere ; but, in every point of a body, even in the view of that great and distinguished philosopher, there are not atoms situated ; since he admita that the most dense bodies contain more vacuity than solid parts ; hence the proposition does not apply in nature ; and it is surprising that Newton's penetrating genius did not perceive this fact. Let only a small distance be admitted to exist between the atoms of bodies, and then a particle may be placed among them, so that it shall be attracted by its contiguous particle, with a force indefinitely greater than it is attracted by all the other particles of the body put togetlier, on the hypotiiesis, that the forces vary inversely as the square of the distance.

The 74th proposition of the Principia will hold good in nature, because il is not requisite in this case, that the forces should be directed to every

X INTRODUCTION.

tract by cold^ and expand by heat^ which indicates repulsion ; the compression^ and subsequent ex* pan^ion of elastic bodies shew the same^. and no bodies are found .altogether void of elasticity. If a convex lens be placed on a plane surface of glass, its weight is not sufficient to bring the surfaces k^Q contact^ nor can this be perfectly effected by. ai|y force we are able to apply ; besides which^ we ba,Y9 innumerable instances of this repulsiye force^ ,|a every depa^rtment of the material world ; destitute of this^ not a single atom of matter has ever be^g £(^und or exhibited ; and^. although^ some phenoni* ena. may possibly appear to be accounted for, iar di^pi^ndently of repulsion, as belonging to every atom of matter; yet the expliqations rest, on feign/ed hypotheses^ . and no phenomenon of nature contradicts tbe supposition that; this principle is as uni- Dorsal as matter itself. Therefore, by the rules* 4^ sound philosophy, we must admit the universal iafluence of both attraction and repulsion.

The attraction, which takes place between the distant bodies of the universe, (and which is clearly aspertained. to be the same as that power eaUed gravitation, by which bodies descend towards the earth,) varies, in. intensity, directly as, the quantity of m^M^er, and reciprocally as tt^e .squi^re of the distance of the attracting bodies. . Sir Isaac Newton has left no doubt on this subject. ; See the Principia, and Cotes* excellent Preface ; and, also^ consult the Authors who have since written on

INTRO DUCTrOK. XI

physical astronomy, where it will be found that the truth of these laws is fully established. But the illustrious Newton and others, have concluded that the attraction, by which the particles or atoms of bodies adhere together, observes a different law, and decreases at a greater rate. The 85th prop. Book i. of tile Principia, is intended to prove this, for which purpose the 70th and 74th propositions are employed.

It should, however, be carefully observed, that the hypothesis of this beautiful theorem requires the attractive forces to be directed to every point of the sphere ; but, in every point of a liody, even in the view of that great and distinguished philosopher, there are not atoms situated ; since he admits that the most dense bodies contain more vacuity than solid parts ; hence the proposition does not apply in nature ; and it is surprising that NeiDton's penetrating genius did not perceive this fact. Let only a small distance be admitted to exist between the atoms of bodies, and then a particle may be placed among them, so that it shall be attracted by its contiguous particle, with a force indefinitely greater than it is attracted by all the other particles of the body put together, on the hypothesis, that the forces vary inversely as the square of the distance.

The 74th proposition of the Principia will hold good in nature, because it is not requisite in this case, that the forces should be directed to every

ZU INTRODUCTION.

point of the body, it being sufficient that the se* veral attracting points be symmetricany arranged. Again it has been said^ that the attraction of cohesion^ at a small increase of distance^ is changed into repulsion ; thos^ when a piece of glass is broken^ and we attempt to replace the fragments^ there is a repulsion^ and the parts cannot be again forced so near together^ as they were before the fracture^ the parts being now removed into the sphere of each other's repulsion. But here ag^in^ we ought to observe^ that the surface and pores of glass and other bodies are replete with a fine elastic fluid, ' which by attraction adheres to those parts of the corpuscles to which it can gain access ; and as soon as the glass, or other body, is broken, the particles of this elastic fluid diffuse them^lves^ by their mutual repulsion, over the surfaces exposed by the fracture, as will be more fully explained in its place ; and these^ atoms of ethereal matter so diffused by their repulsive forces^ wiU prevent the re-union. Various kinds of .attraction 'have been supposed to exists but ev^ry kind, ; not excepting electriical and magneti^^l. attractions, may be explained vnthout hav* ing recourse to any attraction, but that of universal gravitation^ affecting every atom of matter of every sort after the same manner^ and according to the law above mentioned^ as will be seen on consulting the different Sections of this Work.

INTRODUCTION. Xlll

Many opinions have also been entertained respecting these powers, especially repulsion ; some philosophers are persuaded that the atoms of matter have several spheres of repulsion and attraction, succeeding each other alternately : others have supposed, that repulsion acts between the atoms of matter at sensible distances ; and others again conclude, that caloric is the sole cause of repulsion. Caloric has been considered as the only agent in repulsion at minute distances ; it has been called " the repulsive power, which constantly acts in opposition to the power of attraction, or chemical affinity." Parke's Chem, Catechism, p. 88.

Some have considered the law of repulsion as unknown; others state that it varies inversely as the square of the distance ; and others, that at the least, in some cases, it varies inversely as the distance. .It is now generally admitted, that repulsion is as universal as attraction.

Without this power elastic bodies could not recover the figure and slate, which they had before compression. Its action must be perpetuated between every two atoms of matter, otherwise they would adhere inseparably in complete contact; for so minute are the smallest parts of matter known to be, that the attraction between them, if in contact, would be indefinitely great. It cannot, however, be shewn, that repulsion varies by any other law than that of the square of

ZU INTRODUCTION.

point of the body, it being sufficient that the several attracting points be symmetricany arranged. Again it has been said^ that the attraction of cohesion^ at a small increase of distance Js changed into repulsion ; thus, when a piece of glass is broken, and we attempt to replace the fragments^ there » a rep«l,ion, .»d the part, «„„ot be again forced so near together, as they were before the fracture, the parts being now removed into the sphere of each other's repulsion. But here ag^in^ we ought to observe, that the surface and pores of glass and other bodies are replete with a fine elastic fluid,* which by attraction adheres to those^ parts of the corpuscles to which it can ^in access ; and as soon as the glass, or other body, is broken, the particles of this elastic fluid diffuse them^lvesy by their mutual repulsion, over the surfiaces exposed by the fracture, as will be more fully explained in its place ; and these^ atoms of ethereal matter so diffused by their repulsive forces, wiU prevent the re-union. Various kinds of (attraction ihave been supposed to exist, but ev^fy kind^ ; not excepting electriical and magneti(:4l. attractions, may be explained without having recourse to any attraction, but that of universal gravitation, affecting every atom of matter of every sort after the same manner, and according to the law above mentioned, as will be seen on consulting the different Sections of this Work.