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    by the broadest and most natural differences . In chemical action we have evidently something more than simple physical action , and something less than vital action , notwithstanding the vague analogies that may be drawn between these three orders of phenomena on purely hypothetical considerations . The only molecular perturbations which physical activity , properly so called , can produce in bodiesi are nothing more than modifications of the arrangement of the ^ p articles ; and those modifications wh i ch are generally of no great extent are most frequently of a temporary nature ; in no ease is the substance altered . Chemical activity , on the contrary , always produces an essential and permanent change in the very composition of the particles , over and above the alterations in structure and in the state of

    aggregation ; the bodies which were used in the phenomena are not now to beTrecognised , so much has the ensemble of their properties been altered . Finally , physiological phenomena manifest material activity in a degree of energy still greater ; for as soon as a chemical combination is effected the bodies become completely inert j whereas the vital state is characterized , not only by the physical and chemical p henomena which it constantly produces , but also by a double movement , more or less rapid , but always necessarily continuous , of composition and decomposition , capable of sustaining within certain limits of variation , and for a period more or less considerable , the organization of the body , by entirely renewing its substance without end . We thus conceive , in a way admitting of no exception , the

    fundamental gradation of these three essential modes of molecular activity , which true philosophy can never permit of being confounded together . There are also two secondary considerations to be noticed respecting chemical phenomena . First—Every substance is , doubtless , susceptible of chemical action , and this is why chemical phenomena have been properly classedamong general phenomena . They are unlike physiological phenomena , these being peculiar to certain organized substances . But still , in each case of chemical phenomena a specific difference is found . Physical properties , on the other handshow only differences in degree .

    , Second—In order to produce chemical phenomena it is requisite that the antagonistic particles be brought into immediate contact . When the structure of the substance does not spontaneously permit this , it must be artificially attained by liquefaction , The ensemble of the foregoing considerations may be exactly summed up by defining Chemistry as having for its general object , the study of the laws of those phenomena of composition and decomposition , which result from the mutual molecular and specific action , of different substances , natural or artificial .

    There is reason to fear , from the extreme imperfection of this science , that it will not permit , for a long time , of a more exact and more precise definition , capable of characterizing plainly what are in general the indispensible data , and the final unknown terms , of every chemical problem . But the idea of science is always combined with that of prevision in true philosophy , and the final aim of Chemistry ought , therefore , to be thus conceived : —Given , the chemical properties of certain substances , simple or compound , placed in cJiemical relation , under well-defined circumstances , to determine exactly in what their action will consist , and what will be the principal properties of the new products .

    We easily conceive that if such solutions were actually obtained , the three great and fundamental applications of chemical science—to the study of vital phenomena , to the natural history of the terrestrial globe , and , in the last place , to industrial operations—would be thereby rationally organized , instead of being , as at present , the almost accidental and irregular result of the spontaneous development of science ; seeing that in every one of these three general cases the question immediately falls within our abstract formula , the data of which are directly furnished by the particular circumstances of each application .

    In examining more profoundly this rational definition of chemical science , and carrying out the principle of it another step , we shall find it susceptible of an important transformation ; for all the fundamental data of Chemistry could thus be reduced to the knowledge of the essential properties of simple substances solely , which would lead to that of the different immediate or primary combinations , and thence to the most complex and most remote . We should then have to make each simple substance the direct object of experimental study by itself . It may be that there is a certain general and necessary harmony between the chemical and physical properties of each chemicni substance ; but we cannot go the length of saying that this harmony would ever dispense with a distinct and independent chemical examination of each of these substances . But if onco our knowledge of the

    chemical qualities of each simple substance were completed , by observation and experiment ,, all the other chemical problems , notwithstanding their immense variety , would become susceptible of purely deductive solutions , by means of a small number of invariable laws , established by the true genius of Chemistry for the different classes of combinations . . , , Under this point of view compounds naturally present two general modes of classification , both of which necessarily require marked notice . First , The simplicity or the greater or less degree of composition of the

    primary combinations . Second , The number of the combined elements . Now , observation has shown that the higher the order of composition of any substances the more difficult does chemical , action between them become ; the majority of compound atoms belong : to the two first orders ,

    arid beyond the third their combination seems almost impossible- while * under the second point of view , compounds very rapidly lose their stability * in proportion as the number of elements is increased . IVtost frequentlv there is only a simple dualism , and scarcely any body is more than a quaternary . Hence the number of general chemical classes to which this two - fold and necessary distinction Can give room can never be much extended To each of them there would correspond a fundamental law of combination ' which , when applied to any Case in hand , would deductively make known the result from the elementary data . It is to our own radical feebleness and partly to the vicious direction of our intelligence , much more than to

    the peculiar nature of the subject , that we must specially attribute the cause of our being yet so very far from such a method of jphUosophising . However difficult it may appear at present , we ought not to forget that we find it realized , to a certain extent , in a very important though secondary category of chemical researches—the study of proportions . By the aid of a chemical co-efficient , evalued empirically for each simple substance , we are able , in numerous cases , with sufficient exactness , to determine deductively , from a small number of general laws , the proportion according to which the compounds previously known unite in each new product . "Wh y should not all the other branches of chemical study allow in the end of a

    perfect analogy ? We may then sum up these observations by defining Chemistry , in the most rational way possible , as having this for its ultimate object ' . —Given , the properties of all simple substances , to find those of all the compounds which they can form . Chemistry , when compared with the preceding sciences , affords a strong verification of the law that the complexity of the sciences , and their means of exploration , increase together .

    It is here that the first and the most general of the three essential modes of investigation , which we have distinguished in Natural Philosophy , begins to receive its integral development ; until arrived atthis science ^ observation is in fact always more or less partial . In Astronomy , it is necessarily limited to the exclusive employment of a single one of our senses ; in Physics , hearing , and particularly touch , come to the aid of sight ; but taste and smell remain essentially inactive . In Chemistry , 6 n this Contrary ,

    all the senses simultaneously concur in the analysis of its phenomena . We can form a correct idea of the increase of power which results from this convergence , by trying to picture , as far as possible , what would become of Chemistry if it were there necessary to renounce the use of smell and taste—these very often furnishing us with the only characteristics by which we could recognise and distinguish the different effects produced . 3 ut what the philosophical mind ought especially to observe on this subject is , that in this correspondence there is nothing accidental , nor even empirical . Because the true physiological theory of sensation , clearly shows that the apparatus of taste and smell , unlike those of the other senses , acts in an eminently chemical way , and that , consequently , the nature of those two senses specially adapts them for perceiving the phenomena of composition

    and decomposition . 4 With regard to experiment , according to his definition of it , Comte repeats that the part it plays in Chemistry is altogether overrated , great though its efficacy undoubtedly is , and greater though it will be when the science is cultivated more philosophically ; for chemical effects usually depend on too great a concurrence of different influences to make it easy to throw light on the production of them by true experiments . We should have the difficult task of instituting two parallel cases , exactly identical m

    all their characteristic circumstances , save in that one of which we desire to find the value ; this being the fundamental condition of all unexceptionable experiment . The nature of p hilosophical investigations presents a complete obstacle to the purely experimental method , the use o which is almost always illusory there ; and it is in Chemistry , owing to the complication of its phenomena , that we first meet with this same impediment , although to an infinitely less extent . Finally , with regard to the . third fundamental mode of rational exploration , comparison , properly so called , the least general of all ; it is ot importance to consider here , tiiat if this process is essentially destined i physiological studies , its employment first begins to acquire a real etnea ^ y in chemical researchesThe essential condition of this precious nietnou /» /*•¦»«¦»¦

    . A 1 J , L'llV'lJllJlvUl AVOVUJl \< I 1 VUI A *»^ x /» - * fc * v * wjlm * vv ^ - ** ^— —— 'A A . consists in the existence of a sufficiently extended series of analogous d ^ distinct cases , where a phenomenon common to them all is more and m modified , both by simplifications and by a successive and almost continU decrease in the degree of its manifestation . Evidently , p hysiological p ^ nomena can alone give complete scope for the emp loyment of this me But the admitted existence of natural families in Chemistry makes it p - bable that , in the future progress of this infant science , a corrosponc b classification will yet be made , which will lead to the use of the com {! tive method in Chemistry , both being founded on the common j 1011 ^ long tions of uniformity in certain preponderating-phenomena disp layed in a

    scries of different bodies . , mean Chemical investigations enjoy the advantage of a verification by ^ of the double process of Analysis and synthesis . Strictly spotting , process of synthesis , though useful , may be dispensed with when ^ V j ^ of the experiment is to discover the simple elements of a given su ^^ whereas , when the experiment is made to find out what are the c 0 V [^ o ^ which immediately form the given substance , we may in appearanc , ^ them , but in reality have got compounds produced by new combma . ne the course of the process . In the latter case , therefore , synt hesis j » b

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• Citation
  • Leader (1850-1860), June 12, 1852, page 568, in the Nineteenth-Century Serials Edition (2008; 2018) ncse-os.kdl.kcl.ac.uk/periodicals/l/issues/vm2-ncseproduct1939/page/20/