action becomes repellent, and increases as each plane approaches towards the prolongation of the other, a situation which ])roduces the maximiim of repulsion. The supposition which arises in this case is that the action is in proportion to the cosine of the angle of the two planes; hut we have not yet attained such certainty as in the former case.
As for the influence of distance, M. Ampere supposed that, in analogy with Coulomb's law of common electric attraction and repulsion, the action of two conducting elements is always reciprocal to the square of the distances of their middle points. But analogy is not sufficient to conclude upon; and direct observation is out of the ques- tion when the parts taken are infinitely small, and the result sought must be affected by the form and magnitude of the conductors. However, it may be mathematically demonstrated that, in the hypothesis adopted by M. Ampere, the action of a rectilinear conductor, of an indefinite length, upon a magnetized needle, must vary exactly in the inverse ratio of their shortest distance. This consequence has been precisely verified by experi- ment; and it places beyond a doubt the reality of the pro- posed law.
Under this law, electric action would seem to be, mathe- matically, in analogy with that of gravitation. But this case affords a lesson against incaution in transfen-iug to the study of these singular movements the ordinary procedure of abstract dynamics. Gravitation is independent of mutual direction, which is the determining influence in electrical dynamics: and thus the parallel fails. We see, further, how many more difficulties are in the way of the analysis of electric forces than in that of molecular gravita- tion. If this last is, from its complexity, unmanageable excey-)t in the simplest cases, it is no wonder that electrical dynamics has not been mathematically studied further than in one dimension, and never at all in surface. Even this much would be hardly effected but for a last funda- mental idea, established by M. Ampere; that in an infi- nitely small extent, and as long as the distance is not sensibly changed, the electric action is identical for two conducting elements issuing at the same extremities, what- 310 - POSITIVE PHILOSOPHY.
ever may be otherwise their difference of form. Such a pro- perty must introduce valuable analytical simplifications, tending to establish a remarkable analogy between electric, and ordinary dynamic decompositions.
These are the grounds on which the study of the various action of electrized threads proceeds. Among the many dispositions of these conductors, the most interesting case is that of the spiral form; and esjjecially when the turns are very close together. M. Ampere has shown the high importance of this form, in order to imitate, as exactly as possible, the phenomena characteristic of magnetized bodies.'
Physics x^hysics, noticing m turn the as])ects presented by the study of the properties com- mon to all substances and all structures. These are not so much branches of a single study as distinct sciences. Part of our business has been to carry on a philosophical operation, hardly necessary in astronomy, but becoming more and more so as we descend to the more complex sciences; — that of disengaging real science from the in- fluence of the old metaphysical philosoi:)hy, under which it still suffers deplorably, and which manifests itself in Physics through illusory and arbitrary conceptions about the primitive agents of phenomena. I have been able only to indicate the mischief, and where it resides; and I must leave the work of purification to rational philosophers, whose attention will, we must hope, be more and more drawn to this vital question. It is with the same view that I have endeavoured to assign the true application of mathematical theories to the principal branches of physics, pointing out by the way the danger of the excessive sys- tematization which is too often sought by carrying the use ' M. Comte concludes the section on Electricity by a sHglit reference to tlie discoveries of Oersted, Araj;() and otliers, regarding its virtual identity with ail we term tiie magnetic forces. But as the whole of this most interesting and impoi-tant part of Physics has taken a new form siu(;e the date of his work, it lias not, for reasons assigned in tlie Preface, heen thought necessary to repro- duce his remarks in this i)lace. — J. P. N.
CONCLUSION OF PHYSICS, 311 of this powerful instrument further than the complex nature of the corresponding phenomena would fairly allow. While giving my chief attention throughout to the method, I have pointed out, in brief, the principal natural laws relating to each dej^artment of science, discovered by human effort during the two centuries which have elapsed since the birth of Physics, properly so called: and I have shown what gaps are disclosed in the course of such a survey.
Our next study will be of the last science which belongs to the class of general knowledge, or that of inorganic nature. Chemistry relates to the molecular and specific reactions which different substances exert upon each other. It is a more complex, and consequently more imperfect science than those which we have reviewed: but its general character may be perfected, thi'ough the means afforded by its subordination to the anterior sciences.
312 Its nature. VV CHAPTER I.
E have now to review the last of the sciences which relate to the inorganic world. Chemistry has for its object the modifications that all substances may undergo in their composition in virtue of their molecular reactions. Without this new order of phenomena, the most important operations of terrestrial nature would be incomprehensible to us; and thei*e is no other class of phenomena so intimate and so complex. Inert bodies can never appear so nearly like vital ones as when they produce in each other those rapid and jjrofound perturbations which characterize chemical effects. We shall see hereafter that the spirit of all theological and metaphy- sical philosophy consists in conceiving of all phenomena as analogous to the only one which is known by immediate consciousness, — Life: and we can easily understand that the primitive method of philosophizing must have exerted a more powerful and obstinate dominion over chemical l)henomena than any other, in the inorganic world. — We must consider, too, that direct and spontaneous observa- tion must have been applied in the first place only to very complicated phenomena, such as vegetable combustions, fermentations, etc., the analysis of which now requires all the resources of our science: and that the most important chemical phenomena are produced only in artificial circum- stances, which were long in being devised, and very difficult at first to institute. Easy as it is now for even the most ordinary inquirers to use known substances for the dis- closure of new relations, we can hardly imagine the difliculty IMPERFECTION^ AND CAPACITIES OF CHEMISTRY. 313 there must have been, in the infancy of chemistry, in creat- ing suitable subjects for observation: and. we cannot suppose that the ancient investigators of nature could have had energy and perseverance to discover the principal pheno- mena of the science if they had not been constantly stimu- lated by the unbounded hopes arising from their chimerical notions of the constitution of matter. The complex and doubtful nature of the phenomena, in the /.. ^. • first place, and next the difl&culty of getting fection"^^^ at them, are quite enough to account for the tardy and incomplete j)ositivity of chemical conceptions, in comparison with all others in the inorganic region of nature. If, as we have seen. Physics is defective in several respects, much more must that science be so which, being at once more difficult and more recent, seeks the laws of composition and decomposition. Whichever way we look at it, whether speculatively, as to the value of its explana- tions, or actively, as to the previsions which they admit of, this science is evidently the least advanced of all the branches of inorganic philosophy. Indeed, it is hardly possible to call chemistry a science at all Avhile it scarcely ever leads to that precise prevision which is the criterion of perfection in speculative knowledge. We can rarely tell what will be the result of the smallest and fewest modifi- cations introduced among the best explored chemical opera- tions; and while that is the case, however important and numerous may be the facts collected, we are in possession of only erudition, and not science. To supjiose otherwise is to mistake a quarry for an edifice.
It is not to be hoped that chemistry can,-, ever attain a state of rationality so satisfac- tory as that of the sciences which relate to phenomena of a more simple character; and especially that of the eternal type of natural philosophy, — Astronomy. But so much of its inferiority seems to be due to a vicious philosophy, and to the defective education of philosophers, that I cannot but hope that a judicious philosophical analysis may con- tribute to a speedy perfecting of so important a science. This is the conviction that I desire to awaken by the rapid sketch which I propose to offer of chemical philosophy, re- garded in all its essential aspects. Little as can be done 314 POSITIVE PHILOSOPHY.
within the bounds of tliis section, it is possible that some one eminent inquirer may be impressed by the necessity of suljmitting to a new and more rational elabo- ration the fundamental concej)tions which constitute the science.
„-.. First, — what is the general object of Cheniistrv Chemistry? Vast and complex as is its subject, the definition of Chemistry is easier than that of Physics. We are already prepared for it, in- deed, by having contrasted that of Physics with it. It is easy to characterize the phenomena of chemistry, in a direct and marked manner; for all indicate an alteration, greater or smaller, in the constitution of bodies: that is, a compo- sition or decom2:)Osition, and generally both, taking into the account the whole of the substances which participate in the action. Thus, at all epochs of scientific development, since chemistry first became an object of speculative study, chemical researches have steadily manifested a remarkable originality, which has prevented their being confounded with other parts of natural philosophy; even while Physics itself was was mixed xvp, as its title shows, with physiology; which was the case up to a very recent time. — It is by this general character of its phenomena that Chemistr}^ is dis- tinguished from Physics which precedes it, and Physiology which follows it. The three sciences may be considered as having for their object the molecular activity of matter, in all the different modes of which it is susceptible. Each corresponds to one of three successive degrees of activity, which are essentially and naturally distinguished from each other. The chemical action obviously presents some- thing more than the physical action, and something less than the vital. The physical activity modifies the arrange- ment of particles in bodies; and these modifications are usually slight and transient, and never alter the substance. The chemical activity, on the contrary, besides these altera- tions in the structure and the state of aggregation, occa- sions a profound and durable change in the very composi- tion of the particles: the bodies which occurred in the phenomenon are no longer recognizable, — so much has the aggregate of their properties been disturbed. — Again, phy- siological phenomena show us the molecular activity in a CHARACTER AND 'CONDITIOX OF CHEMICAL ACTIOX. 315 much higher degree of energy; for, as soon as the chemical combination is effected, the bodies become, once more, com- pletely inert; whilst the vital state is characterized, over and above all physical and chemical effects, by a double continuous motion of composition and decomposition, adapted to maintain, within certain limits of variation and of time, the organization of the body by incessantly renew- ing its substance. This is the gradation, which no sound philosophy can ever confound, of the three modes of mole- cular activity.
Two more characteristics of this science must be pointed out: one relating to its nature, and the other to its general conditions.
Chemistry would not be classed among the Specific cha- inorganic sciences unless its phenomena were racter of its genei'al; that is, unless every substance were action, susceptible of chemical action, more or less. And it is be- cause chemistry is thus radically different from physiology that it ranks as the last of the inorganic sciences, — physio- logical phenomena being, by their nature, i^eculiar to cer- tain substances, organized in certain modes. Nevertheless, it is incontestable that chemical phenomena present, in every case, something specific, or, to use Bergm aim's ener- getic expression, elective. Not only does each material element produce chemical effects which are altogether peculiar to it, but it is the same with their innumerable combinations of different orders, among the most analogous of which certain fundamental diiferences are observable, even so as to be adopted as their characteristics. While therefore physical differences among different bodies are those of degree only, chemical properties are specific. Phy- sical properties afford the common foundation of material existence; and it is by chemical properties that individu- ality is manifested.
The other characteristic relates to the p,.. mode of chemical action. The immediate ac^t'ion ^*'" ° contact of antagonistic particles is absolutely necessary to chemical action; and therefore one at least of the substances concerned must be fluid or gaseous. When this condition does not already exist, it must be arti- ficially procured by liquefying the substance. It is the 316 POSITIVE PHILOSOPHY.
earliest axiom in the science, that comhination cannot take place, except under this condition; and there is not an in- stance upon record of chemical action between two solids, unless at a temjjerature which obscures the true state of as^gregation of substances; and the action is never so j^owerful as when both substances are liquid. These facts establish the eminently molecular character of chemical effects, and especially in comparison with physical effects. The distinction from physiological effects is, though less marked, as real, the latter requiring, as we shall see here- after, the junction of solids with fluids. „ ^.. The definition of Chemistry, then, is that it relates to the laws of the phenomena of composition and decomposition, which result from the molecular and specific mutual action of difl'erent substances, natural or artificial.
It will be long, we must fear, before a more precise defi- nition than this can be given. Meantime, however incom- plete, the most rational that can as yet be offered is of imjjortance as far as it goes. In this view, and connecting, as usual, the consideration of science with that of prevision, the aim proposed should be this: — the characteristic pro- perties of substances, simple or compound, being given, and those properties being placed in a chemical relation in well-defined circumstances, to determine in what their action will consist, and what will be the chief properties of the new products. This problem is, at all events, determi- nate; and nothing contained in it could be omitted without its ceasing to be so; and the formula therefore contains nothing superfluous. On the other hand, if we could obtain such solutions as are indicated, the application of chemistry to the three great objects, vital phenomena, the natural history of the globe, and industrial operations, would be rationally organized, instead of being, as now, the almost accidental result of the spontaneous development of science. Each question would at once be referred to our formula, the data of whi<-h would be supplied by the circumstances peculiar to the apj^lication. Far distant as we are from being able thus to conduct our inquiries, this is the end to be kept in view: and chemists all agree that the most advanced portions of their science are those few ELEMENTS AND THEIR COMBINATIONS. 317 and simple questions in which this aim has been more or less completely attained.
By a continued application of this method, all the data must finally be reducible to the knowledge of the essential proj^erties of simple substances, which would lead to that of the different immediate principles: and consequently, to the most comj^lex and remote combination. As for the study of the elements, that must, of course, -p, be a matter of direct, experimental elabora- tion, divided into as many parts as there ai*e undecomposed substances. Whether or not it may be possible to discover, by rational methods, relations between the chemical pro- perties of each element and its aggregate physical proper- ties, we must lay down as indispensable a direct exploration of the chemical characters of each element. This general basis once obtained from experiment, all other chemical problems must be susceptible of a rational solution, under a small number of invariable laws.
The classes of combinations naturally divide ^, i •. f themselves into two, according, first, to the simplicity, or the greater or less degree in which the im- mediate pi'iuciples are compounded: and, secondly, the number of elements combined. Chemical action is observed to become more difticult the more substances are com- pounded: the greater part of compound atoms belong to the first two orders; and beyond the third their comjiosition seems almost impossible: and, in the same way, in regard to the number of elements, combinations lose their stability in proportion as the elements are multiplied: there are usually only two; and scarcely any body involves more than four. Thus, the number of chemical classes must always be very small in regard to the distinction under notice: and each of them must have a corresponding law of combination, according to which the result might be certainly auticii^ated through a knowledge of the data. This would be the scien- tific perfection of chemistry. Our prodigious remoteness from such a state is ascribable to the feebleness of our faculties, and, in an accessory way, to their vicious direction. We must remember that the great aim has begun to be fulfilled in one secondary department of chemical research, — the study of proportions, as we shall see hereafter.
318 POSITIVE PHILOSOPHY".
What has been done in that one category makes us ask why an analogous perfection should not be attained in other departments. We may sum up this account of the requi- Rational sites, with the fully rational definition of definition. Chemistry, that it has for its object, — the properties of all simple bodies being given, to find those of all the compound bodies which may be formed from them. Every science falls short of its definition: but a real defi- nition is the first evidence that a science has attained some consistency: it then measures its own advancement from one epoch to another; and it always keeps inquirers in a right direction, and supports them in a philosophic progress.
-_.. Looking now at our means of investigation, vestio-ation ^^^ shall find that in chemistry the law holds good that the complication of phenomena coincides with the extension of our means of inquiry. ^,.,. Here Observation begins to find its full development. Up to this time it has been more or less j^artial. In astronomy, it is confined to the sense of sight: in physics we use hearing and touch also; and chemistry employs, besides these, taste and smell. How much is thus gained we may know by imagining what would become of chemistry, if we were without taste and smell, which are often the only means by which we can recognize effects produced. The important thing to observe under this head is that thei'e is nothing acci- dental, nor even empirical, in such a correspondence; for, as we shall hereafter see, the sound physiological theory of sensations shows that the apparatus of taste and smell, unlike that of the other senses, operates in a chemical manner, and thus shows these two senses to be specially adapted for the percej^tion of phenomena of composition and decomposition. -n,., As for E'ajBenmewi, it is enough tosay that the greater number ot cliemicai ]inenomena, and especially the most instructive, are of artificial jiro- duction. Still, we must remember that the essential character of experimentation consists in the institution, or the choice of the circumstances of the phenomenon, in order to a more evident and decisive investigation. This j)ro- MEANS OF INVESTIGATION. 319 cess is more difficult in cliemistry than in physics, because it is more difficult to institute two parallel cases, undis- turbed by the intrusion of irrelevant influences; and yet this is the fundamental condition of experimentation. On this account, I dissent from the ordinary supposition that the experimental method is more appropriate to chemical than to physical researches. Though this is my view, and though the greater advancement of physics gives it the advantage over chemistry, in the use of experiment, I can liave no doubt of the powerful influence of experimentation in chemistry, independently of its having supplied new subjects of observation. From the early days of the science, the immortal series of Priestley's experiments, and yet more, those of Lavoisier, have offered admirable models, almost comparable to the most perfect researches in physics, and qviite enough to prove that there is nothing in the nature of chemical phenomena to prevent the extended and luminous employment of the experimental method.
The third means. Comparison, which we p have before seen to be inapplicable in Astro- nomy, and of especial use in Physology, begins to have a real use in Chemistry. The essential condition of this valuable method is that there shall be an extended series of cases, analogous but distinct, in which a pheuomenon shall be modified more and more, whether by successive simplifications or gradations. It is evident that this can take place fully only with regard to vital phenomena; accordingly, it is only by physiological analysis that a clear idea of its value can be obtained. But chemical phenomena approach those of physiology nearly enough, not onlv to demand this method, but to indicate that without it the science can never find the road to perfection. The existence of natural families in chemistry is now admitted by the best inquirers: but the classification remains to be made. The need of the classification must lead to the use of the comparative method, both being based on the common consideration of the uniformity of certain preponderant l^henomena in a long series of different bodies. There is even such a connection between the two orders of ideas that the construction of a natural chemical classification is impossible without a large aj)plication of the comparative 320 POSITIVE PHILOSOPHY.
art, as the physiologists understand it; and conversely, comparative chemistry cannot be regularly cultivated with- out the guidance of some sketch of a natural classification. Chemistry is at present only a nascent science; general methods are as yet scarcely recognized in connection vrith it; and only a very few researches afford an example of the comparative method; but I am persuaded not only of the fundamental suitability of that method in chemistry, but of its application, before very long, to the perfecting of the science. Such an anticipation, somewhat preceding the spontaneous development of any science, may be a contri- bution to its actual progress.
Chemical ana- All the means employed are subject, — lysis ami syn- especially, but not solely in chemistry, — to a thesis. verification by the precise collation of the two procedures of analysis and synthesis; — -or, (as these terms have been corrupted by metaphysical uses) compo- sition and decomposition. — Every substance which has been decomposed must evidently be capable of recompo- sition, whether the process be otherwise practicable or not. If the inverse operation reproduces precisely the primitive substance, the chemical demonstration is complete. Unfor- tunately, the vast extension of chemical resources in this century has had a much stronger bearing on analytical powers than synthetical means; so that there is at present little proportion and harmony between the two methods. — Such harmony is indispensable to the establishment of certainty in some cases, as we see when we duly distinguish two widely differing kinds of chemical analysis: the pre- liminary, consisting of the simple separation of the imme- diate principles; and the final, leading to the determination of the elements, properly so called. Though both are essential to chemical research, the first is of the most im- portant and extensive use. The elementary analysis might be spared a synthetical verification, — because the compo- ■sition of the reacting substances may be compared with the results obtained, thus indicating the composition of the