A Preliminary Discourse on the Study of Natural Philosophy 9780226327785

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A PRELIMINARY DISCOURSE ON THE STUDY OF

NATURAL PHILOSOPHY

A PRELIMINARY DISCOURSE

ON THE STUDY OF

NATURAL PHILOSOPHY

John F. W. Herschel With a new Foreword by

Arthur Fine

The University of Chicago Press

Chicago & London

This is a facsimile of the 1830 edition published as volume I of Dionysius Lardner's Cabinet Cyclopaedia (1832).

The University of Chicago Press, Chicago 60637 The University of Chicago Press, Ltd., London

© 1987 by The University of Chicago All Rights reserved First published in 1830 University of Chicago Press Edition 1987 Printed in the United States of America 95

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Library of Congress Cataloging in Publication Data Herschel, John F. W. (John Frederick William), Sir, 1792-1871. A preliminary discourse on the study of natural philosophy. Reprint. Originally published: London: Printed for Longman, Rees, Orme, Brown, Green, andJ. Taylor, 1830. (The Cabinet cyclopaedia; v. 1) Includes index. 1. Science-Philosophy. 2. Science-History. 3. Physics-History. 4. Astronomy-History. I. Title. II. Series: Cabinet cyclopaedia; v. 1. Q175.H427 1987 501 87-5985 ISBN 0-226-32777-9 (pbk.)

FOREWORD

In some eras the popular image of science is associated with a single name: Newton in the seventeenth century, Einstein in our own. Nineteenth-century England is represented by John Herschel. A brilliant mathematician, Herschel was also an accomplished chemist, whose investigations at the interface of chemistry and optics paved the way for the development of modem photography (a word coined by Herschel in 1839). His most acclaimed successes, however, were in astronomy, especially for studies of double stars, where his work was recognized in prizes awarded by the French Academy, the Royal Society, the Astronomical Society, and others. In these studies Herschel developed and applied new graphical methods for showing how the relative motion of the two stars in a binary system closely followed the laws of Newtonian celestial mechanics. In Herschel's time this accomplishment was widely regarded as the final triumph in the demonstration that the laws of physics had I,lniversal scope. Herschel was a person of great learning and energy, and he complemented his scientific research with an active engagement in issues of educational reform and public policy (being an early advocate of decimal coinage). His writings include hundreds of scientific papers, seven books, and several important encyclopedia articles. He also translated a number of literary works, among them some of Schiller's poems put into English hexameter, Dante's Inferno, and

Foreword Homer's Iliad. Two of the encyclopedia articles were commissioned as separate volumes in Dionysius Lardner's Cabinet Cyclopedia, a work intended for a semi-popular audience including the senous "amateurs" of nineteenth-century science. One of these Cyclopedia volumes developed into a celebrated treatise, Herschel's Outlines of Astronomy (1849). The other, volume one of the Cyclopedia, was reprinted several times, widely read by his peers, and became a standard reference work on the methodology of science. It is Herschel's A Preliminary Discourse on the Study of Natural Philosophy (1830).

John Herschel (Sir John Frederick William, 17921871) was born in Slough, England, in the county of Buckinghamshire on March 7, 1792. He was an only child, the son of Sir William Herschel (1738-1822) and the former Mary Baldwin Pitt. His father, Sir William, was the discoverer of the planet Uranus and one of the most illustrious astronomers of his time. John Herschel married relatively late in life, in 1829, to Margaret Brod~e Stewart, with whom he had twelve children. Perhaps following Newton's example, Herschel's last important public activity was as master of the mint (1850-56). After holding that office he retired to work on catalogues of nebulae, star clusters, and double stars. He died on May 11, 1871, was mourned by the nation, and was buried next to Newton in Westminster Abbey. For the most part John Herschel's early education was conducted privately near his home, although he did attend Eton, briefly, around age eight. While at home he was certainly influenced by the astronomical

Foreword industry carried on there by his father, Sir William, and his aunt, Caroline Lucretia Herschel (17501848). At age seventeen Herschel entered St. John's College, Cambridge, where he concentrated on the study of mathematics. He completed his examinations at Cambridge in 1813, taking honors as "first senior wrangler," the highest distinction awarded. In the same year St. John's elected him a fellow, a position he retained until his marriage. Also in 1813 he was elected a fellow of the Royal Society for papers in applied mathematics, the last of which his father had the pleasure of presenting to the society. During Herschel's time at Cambridge, he made the acquaintance of William Whewell (1794-1866), also, then, a student of mathematics and later, more philosopher than scientist, the author of a competing popular treatise on scientific method, The History of the Inductive Sciences (1857). Although they disagreed on the relative weight to be assigned the empirical versus the ideational elements in science, with Herschel more on the Humean, empirical end of the spectrum and Whewell more on the Kantian side, these two men were to become, in Whewell's words, "friends of a lifetime." While at Cambridge Herschel also formed a lasting friendship with Charles Babbage (1792-1871), whom we recognize today as an important modern pioneer in the design of calculating machines, and with George Peacock (17911858), an educational reformer and later the Lowndean Professor of Astronomy at Cambridge. These three founded the Analytical Society devoted, as Herschel would say, to the replacement of "dot-age" by "d-ism"; that is, to replacing the fluxional dot no-

Foreword tation (jr) of Newton, in the differential calculus, by the (dy/dx) notation of Leibniz. Thus Herschel and his friends led the reform that opened Great Britain to the important discoveries and methods of continental analysis which, in turn, gave rise to the brilliant nineteenth-century school of British mathematical physics (A. Cayley, G. Green, W. Hamilton, lC. Maxwell, G.G. Stokes, J.T. Sylvester, W. Thompson, and others). In 1814 Herschel followed the example of several Cambridge mathematicians who had pursued successful careers in the law, and moved to London to begin a legal apprenticeship at· Lincoln's Inn. In London, however, he became acquainted with and influenced by William Hyde Wollaston, whose scientific work, like Herschel's, included important discoveries in chemistry (e. g., the elements palladium and rhodium) and in optics (e. g., the dark lines in the solar spectrum, and the invention of the reflecting goniometer and of the camera lucida). There he also met the wealthy amateur astronomer James South, with whom he later (1821-23) collaborated in reexamining and extending some of William Herschel's observations on double stars, work that was recognized by prizes both from the French Academy (1825) and from the Astronomical Society

(1826). In 1815 John Herschel returned from London to Cambridge, where he applied for the chair in chemistry. Failing in that, he took up a teaching post as sublector at St. John's, pursuing his researches there and taking an M.A. in 1816. Herschel then returned home to Slough. As he later said, he was most inclined toward the study of chemistry and optics but

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increasingly he found the influence of his father, and the call of filial duty, moving him ever more strongly toward astronomy. Indeed in 1820, with his father's help, Herschel completed a mirror for a reflecting telescope, eighteen inches in diameter and with a focal length of twenty feet. Subsequently refined, it was with this instrument that Herschel made his most important astronomical observations. From 1816 to 1833 Herschel carried on research in mathematics, optics, chemistry, and astronomy. In 1821 the Royal Society presented him with its Copley medal for his mathematical contributions. His optical investigations included a searching theoretical analysis of the wave versus the particle theory of light, presented in articles on light (1827) and on sound (1830) for the Encyclopedia Metropolitana. He also investigated properties of compound lenses, the polarization and birefringence of crystals, and the interference of light and sound. In 1819 Herschel discovered that the salts of silver were soluble in "hyposulphite of soda" (the older name for Na2S2 03.5H2 0, sodium thiosulphate penhydrate). This is the photographer's "hypo," whose use Herschel pioneered. (He is also responsible for the photographic terminology of "positive" and "negative. ") During this period Herschel continued with his astronomical observations at Slough, following up his father's work on the observation of nebulae, clusters, and double stars. His memoir On the investigation of the orbits of double stars won a medal from the Royal Society in 1833, and also much popular acclaim. That same year Herschel brought out a catalogue of 2,307 nebulae and clusters, and by 1836 he had issued no less than six catalogues of double stars (3,346 sys-

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terns, in all). Somehow, amid all of this scientific industry Herschel found time for travel abroad, where he mixed walking tours and sightseeing with visits to virtually all the important European scientists of his generation. He also found time for marriage and family life. In 1833 Herschel resolved to complete a survey of the heavens by doing for the southern skies what he and his father had achieved for the north. So he proceed~d to move himself, his own telescope ("so as to give a unity to the results of both portions of the survey") and his family to Africa, settling in the colony near Cape Town. For the next five years he carried on his astronomical work there, along with activities in botany and meteorology. He also helped devise a new educational system for the colony. The astronomical work involved surveying 3,000 areas of the southern sky, counting nearly 69,000 single stars and 4,000 multiple systems. The data reduction and analysis occupied Herschel for nearly a decade, following his return to England in 1838. The extraordinary Cape Obseroations, published in 1847, represents the scientific labor of a single individual, labor of a magnitude unlikely ever to be repeated. The last decades of Herschel's life were devoted to public service, general scientific writing, his translation of the Iliad and, as always, the star catalogues. His final work, a catalogue of 10,300 double stars, appeared shortly after his death in 1871.

The Preliminary Discourse of 1830 stems from one of the most fruitful and varied periods of Herschel's scientific career. It was a period of prestigious

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awards and of personal scientific achievement. It was also just at the beginning of his life with Margaret, a time when Herschel was filled with enthusiasm for science and passion for life. This spirit of enthusiasm enlivens the pages of the Discourse, blending easily with what we now identify as the progressive faith of the Victorian era. The Discourse opens with an engraving of Francis Bacon (1561-1626), who is eulogized in sections 96-106 as the theoretician of a new scientific age. The Discourse closes with a chapter devoted to explaining the grounds for what Herschel sees as the more rapid advance of science in his time than in any other. The reader will find citations there from the popular essays of a musician, the English composer William Jackson (17301803). Herschel's father was also a composer and a music teacher before he turned astronomer, and so perhaps his father was on his mind as Herschel framed his own statement of the progressive faith in that concluding chapter, "In whatever state of knowledge we may conceive man to be placed, his progress towards a yet higher state need never fear a check, but must continue till the last existence of society" (section 392). The Discourse, however, IS more than a sustained ode to the progress of science and humankind. It is also a careful analysis and explication· of what Herschel regards as the principles and methods of scientific investigation, told from the perspective of someone himself engaged successfully and actively in scientific work, both at the theoretical level and at the level of experiment or observation. The framework of Herschel's story is Baconian; that is, he seeks to show how scientific knowledge is grounded

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in empirical investigation, and how it relates to the practical affairs of society. But unlike Bacon, Herschel's attitude toward the theoretical and hypothetical aspects of science is unambiguously affirmative. Indeed in the course of articulating the basis for his own model of an empirically rooted hierarchy of laws and high-level theories, Herschel explains the elaborate feedback loop linking inductive generalization with the deductive testing of consequences, a conception that is familiar to us all these days as "the hypothetical-deductive method." The Discourse is divided into three parts. In Part I Herschel seeks to justify the study of "natural philosophy" (i.e., science) on its own grounds against the charge that, as a theoretical activity, it tends to undermine religion and is therefore morally dangerous to pursue. He also defends against the charge that, as a practical activity, science is merely an instrument contributing to our "pampered appetites" (section 7) for the material things of life. To the contrary, using (in part) a curious argument from atomism (section 28), Herschel contends that science necessarily supports religion and subverts materialism. The general picture of science that emerges from the discussion is of an activity whose pursuit actually enhances our moral stature, and whose practical benefits Herschel ties up not just with a better standard of living but also with a democratization of society at large, since the "fruits of science are in their nature diffusive, and cannot be enjoyed in any exclusive manner by a few" (section 62). The reader familiar with the classical arguments for free expression, in terms of a marketplace of ideas, for example, as later expressed in John Stuart Mill's On Lib-

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erty (1859), will find similar arguments deployed by Herschel against scientific elites and in aid of the public dissemination and demystification of scientific expertise (section 63). Indeed one of the most striking features of Herschel's Baconian setting of the scientific enterprise in Part I is his emphasis on science as a community activity, both as generated by a community of coworkers and as generated for the community at large. Thus Herschel takes very seriously his own characterization of science as "the knowledge of many, orderly and methodically digested and arranged so as to become attainable by one" (section 13). For Herschel, science is foremost a human and social enterprise. Part II of the Discourse moves from this general conception of science to its epistemology and methods. Herschel's epistemological orientation is clearly toward the empiricist tradition inherited from Bacon; that is, Herschel takes for granted that experience is the "only intimate source of our knowledge of nature and its laws", (section 67). Moreover, given Hersch~Vs emphasis on the social character of science, for him "experience" refers to the collective experience of mankind. Nevertheless there is also a significant rationalist side to Herschel's thinking, and of the sort often associated with Bacon's younger continental contemporary and methodological rival, Rene Descartes (1596-1650). Descartes had argued that each of us has an innate and natural capacity for knowledge, the so-called "light of nature" that, according to Descartes, was /placed in us by God. The problem of acquiring knowledge of nature, then, was just that of how to free our minds, so as not to interfere with the operation of this inn~te capacity. Thus

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Descartes proposed his famous criterion, that whatever we conceive of "clearly and distinctly" must be so. From this rationalist perspective one could expect a continual growth in knowledge as a natural outcome of proceeding methodically and carefully, and keeping our minds clear. In Herschel (as, indeed, in Bacon as well) we find a blend of empiricism with a tendency toward this sort of rationalism. He writes, "To experience we refer, as the only ground of all physical enquiry. But before experience itself can be used with advantage, there is one preliminary step to make, which depends wholly on ourselves: it is the absolute dismissal and clearing the mind of all prejudice" (section 68; see also section 108). An important theme that links empiricism with rationalism is the idea that knowledge has a foundation (or "ground" as Herschel often puts it). To be sure, the empiricist foundation is in sense experience, whereas the rationalist one involves innate capacities of the mind (or "first principles" of thought). But whether from the bottom up or from the top down, the idea of a foundation motivates the concept of progress through the application of the scientific method, and leads one to think that the scientific method itself constitutes a coherent subject, one worthy of separate investigation apart from a mere survey of the various methods of the different sciences. Herschel simply presupposes this foundationalist blend of empiricism and rationalism without examination or defense. It is the background against which his account proceeds. According to Herschel science originates in observation and experimentation, these being distinguished as more passive (observation) versus more active (experimentation). Herschel favors the active, and holds

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that science began really to advance only when investigators carefully started to intervene in nature experimentally, and to judge the results. The results are how things appear to us, the phenomena, and they are in general complex, requiring analysis into their constituent parts. Herschel gives as an illustration one of his favorite topics, the phenomenon of sound (section 79). The analysis has to do with how sound is produced, communicated and, finally, experienced. That is, what Herschel illustrates as an analysis of a phenomenon into constituent parts amounts to an explanation of the phenomenon in terms of causes and natural laws. Herschel regards a law of nature as "a statement . . . of what will happen in certain general contingencies" (sections 80 and 89) or, equivalently, as a statement of an invariable connection (sections 91 and 92), and he takes causes (or causal factors) to be what grounds the truth of such law-statements. According to Herschel, the search for causes and laws is one of the prime goals of science and, as we have seen, thinking in terms of causes and laws is threaded throughout the whole scientific enterprise, right from its ground in observation and experiment. This can lead to problems, however, in reporting observations or experimental results insofar as extraneous causal or theoretical language may infect the reports, making it difficult to get at the fact of the matter (section 125). Thus Herschel's account of observational methods is delicately balanced between, on the one side, the recognition of the necessity for a theoretical orientation and, on the other, the recognition of the dangers with regard to objectivity that can result from such an orientation. There is a simi-

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lar tension that Herschel brings out in his discussion of classification (Chapter V, Part II), which is the next step up from observation. Herschel sees clearly that the grouping of natural phenomena into similarity classes must employ knowledge of constituent causes and lawlike connections. At the same time, he is well aware that such classification is also necessary in order to establish any causal or lawlike connections at the outset. Herschel proffers no magical solution for these dilemmas of practice, except for a general counsel of care, an emphasis on quantitative methods where feasible, and good sense. In noticing the issues, howev"er, Herschel saw farther than many of his contemporaries, and many of ours. In Chapter VI of Part II Herschel articulates a set of general rules for determining causes. In this he follows Bacon and David Hume (Part III, Book I of the Treatise, section 15). Herschel's rules are the material from which Mill developed his own wellknown five "methods" (or "canons") of induction, in A System of Logic (1843). They, in tum, were criticized by Herschel's friend Whewell in Of Induction, With Especial Reference to Mr. J. Stuart Mill's System of Logic (1849). Ironically, Whewell's criticism brings the discussion round full circle. Whewell criticizes Mill's methods because they simply take for granted a preliminary analysis of the phenomena, one which would itself require the use of inductive methods; i.e., Whewell criticizes Mill for ignoring the very circularity in the conduct of causal analysis that Herschel had seen so clearly. According to Herschel's account, the rules for determining causes were equally rules for getting at the low level laws and generalizations codifying the causal connections.

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Once the laws were articulated in this inductive manner, Herschel sought to use them to explain further phenomena; that is, to explore the consequences of the laws deductively. In this regard he emphasizes "that it is very important to observe that the successful process of scientific enquiry demands continually the alternate use of inductive and deductive methods" (section 184). This is the feedback loop referred to earlier, by means of which Herschel connects the discovery of laws with their testing and verification. We can summarize Herschel's conception of scientific method as follows. We begin with observation and experiment, using analogies to help sort the results into causally relevant classes (which he calls "general facts" [section 94]), and then by comparing these classes we arrive at low-level laws. Proceeding from this stage via the same methods of causal analysis, we move to more general groupings and then to laws of wider scope. This process repeats itself through many stages until we arrive at very broad scientific theories. Running in tandem, all along this inductive line, are feedback mechanisms which check and correct the classifications and putative laws at each stage. They involve deductions of the consequences and their comparison with new observational data. As the inductive hierarchy builds up, Herschel notes that there is a natural tendency for the labor to divide between experimental work and work that is of a more theoretical kind (section 126). Thus Herschel's inductive scheme suggests an explanation for the division of labor that we see in SCIence. In his discussion of "residual phenomena" (sections 158-61), Herschel recognizes that the com-

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parison of the law or theory with the data may be inconclusive insofar as one fails to account for all the observed phenomena. When this occurs, we may simply have to shelve what is unexplained, hoping to come back to it at a later stage of development. Similarly, Herschel recognizes that even when many consequences of a theory are well-confirmed, it may still be prudent to suspend judgment concerning the finer details of the theoretical story so that even confirmation may be inconclusive (section 216). However, Herschel does not treat the question of exactly how a "correction" is made when the deductive consequences of a law or theory do not fit the observations. Hence he misses one of the central problems of twentieth-century philosophy of science, the Poincare/Duhem problem concerning falsification and the introduction of ad hoc hypotheses. Nevertheless, Herschel is quite sensitive to the inconclusive character of the self-correcting mechanisms that he does discuss. In fact, his neo-Baconian scheme for arriving at theories inductively is a rather looser and more open-ended scheme than talk of induction and "the scientific method" might suggest. In Chapter VII of Part II the open-ended character of science emerges even more clearly. For there Herschel is concerned with hypotheses and theories that postulate "hidden processes" in order to explain and analyze phenomena, for example, theories about the nature of radiation (e.g., heat or light). In section 210 Herschel recognizes that although we may arrive at such theories by means of the articulated stages of induction, we may just as legitimately arrive there simply "by forming at once a bold hypothesis." All that matters is that we test the hypothesis by pursuing its empirical consequences to the finest details.

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Thus the justification of a hypothesis need not always depend on whether its discovery has an inductive pedigree although, Herschel adds, "There is no doubt, however, that the safest course, when it can be followed, is to rise by induction[ s] . . ." (section 217). The reference to a "safest course" in this passage reminds us that the goal in a scientific investigation, as Herschel conceives it, is to discover the truth of the matter. Can we, then, take a well-confirmed and tested theory that invokes hidden processes as true? Do our methods of verification, which amount to checking the empirical consequences, justify us in believing that the postulated hidden structure is real? Herschel hedges his answer to these questions. On the one hand he says that, given the weight of evidence, we "cannot refuse to admit" such a theory. On the other hand, perhaps it would be prudent to admit it as only truth-like, which is to say that we do not affirm its literal truth but merely accept it as empirically adequate (section 220). Herschel's emphasis here is on the utility of such hypotheses and theories at the empirical level, where they may provide a reliable scaffolding for the organization of data and low-level laws. His worry is that we may "quite mistake the scaffold for the pile" (section 216). Thus with regard to the reality of hidden entities, Herschel's attitude is an instrumentalist one: If well confirmed, accept the theory that postulates them as a reliable guide to the phenomena, but do not necessarily believe it. This instrumentalism, however, does not sit easily with Herschel's faith in the continued progress of science toward its goal of finding the truth about nature. In the very last sentence of the Discourse, as though to address this unease, Her-

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schel invokes simplicity as the criterion "on which the mind rests satisfied that it has attained the truth." Part III of the Discourse turns from philosophy of science to history of science. In these chapters Herschel illustrates his methodological precepts by sketching the development of the physical sciences of his day. No doubt these chapters were also intended as appetizers for the more detailed lessons in science that were to follow in future volumes of the Cabinet Cyclopedia. It must be said that some of Herschel's historical forays in Part III are appalling. This is especially true of Chapter III, on astronomy. There Herschel begins with the familiar Baconian tirade against Aristotle, as "impeding progress," and then proceeds to tell the subsequent history as though it were a case of pure induction from the data, unfettered by hypotheses or theories, and as though the whole historical record led in a simple straight line directly to Newton's celestial mechanics. By contrast, Herschel's discussion of the wave versus the particle theory of light, in Chapter II, Part III is sensitive and subtle. Herschel himself had struggled through the competing experiments and theoretical refinements in this area, coming down, in the end, on the side of the wave theory. He retells this story brilliantly, and even follows his own instrumentalist precepts by recognizing that although the weight of evidence does seem to favor the wave theory we should nevertheless be wary of accepting that as the truth of the matter. In view of the revival of a particle theory in Einstein's light quantum hypothesis of 1905, and the subsequent history of the so-called wave/particle duality, Herschel's caution here seems well placed. The Discourse concludes with a chapter

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reflecting on the mechanisms that Herschel sees as aiding the rapid progress of science. In this discussion he returns to his emphasis on community aspects of science: the role of public education, periodicals and scientific societies, and the general interplay between science and society at large. This brief introduction to Herschel's philosophy of science has emphasized some of his insightful contributions to the subject, as well as some of the uneasy ways in which Herschel's ideas straddle contrasting positions. For a scientist, insightful hedging may be the natural attitude toward science. This was certainly the case with Einstein, whose description of the scientist as philosopher might well have taken Herschel's Discourse as its model: (The scientist) must appear to the systematic epistemologist as a type of unscrupulous opportunist. He appears as realist insofar as he seeks to describe a world independent of the acts of perception; as idealist insofar as he looks upon the concepts and theories as the free inventions of the human spirit (not logically derivable from what is empirically given); as positivist insofar as he considers his concepts and theories justified only to the extent to which they furnish a logical representation of relations among sensory experiences. He may even appear as Platonist or Pythagorean insofar as he considers the viewpoint of logical simplicity as an indispensable and effective tool of his research. (A. Einstein, Albert Einstein: Philosopher-Scientist, ed. P.A. Shilpp [Open Court: LaSalle Illinois, 1949], p. 684.)

Arthur Fine

PRELI.MI.iYARY DISCOURSE

.ott

1!bt ~ltu~~ 4tf

NATIDTmAJt Jf18UC]t@$@]?>DY ~

~~ JOHN FREDERICK WILLIAM HERSCHEL,ESQ.A.M. LATE FELLOW OF S'!" .JOHN'S COLLEGE,CAMBRIDGE.&,!e, 8 acres, and medium depth about 20 feet. It was proposed to drain it by running embankments across it, and thus cutting it up into more manageable portions to be drained by windmills.

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Holland what might be accomplished by the constant agency of the desultory but unwearied powers of wind. But the Dutch engineer measures his surface, calculates the number of his pumps, and, trusting to time and his experience of the operation of the winds for the success of his undertaking, boldly forms his plans to lay dry the bed of an inland sea, of which those who stand on one shore cannot see the other.(56.) To gunpowder, as a source of mechanical power, it seems hardly necessary to call attention; yet it is only when we endeavour to confine it, that we get a full conception of the immense energy of that astonishing agent. In count Rumford's experiments, twenty-eight grains of powder confined in a cylindrical space, wldek it justfilled, tore asunder a piece of iron which would have resisted a strain of 4oo,000Ibs.t, applied at no greater mechanical disadvantage. (57.) But chemistry furnishes us with means of calling into sudden action forces of a character in. finitely more tremendous than that of gunpowder. The terrific violence of the different fulminating compositions is such, that they can only be compared to those untameable animals, whose ferocious • No one doubts the practicability of the undertaking. Eight or nine thousand chaldrons of coals duly burnt would evacuate the whole contents. But many doubt whether it would be profitable, and some, considering that a ft!w hundreds of fishermen who gain their livelihood on its waters would be dispossessed, deny that it would be dainWle. t " Experiments to determine the Force of fired Gunpowder." Phil, Trans. vol. lxxxvii. p. 254. et seq.

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strength h~s hitherto defied all useful management, or rather to spirits evoked by the spells of a magician, manifesting a destructive and unapproachable power, which makes him but too happy to close his book, and break his wand, as the price of escaping unhurt from the storm he has raised. Such powers are not yet subdued to our purposes, whatever they may hereafter be; but, in the expansive force of gases, liberated slowly and manageably from chemical mixtures, we have a host of inferior, yet still most powerful, energies, capable of being employed in a variety of useful ways, according to emergencies. • (58.) Such are the forces which nature lends us for the accomplishment of our purposes, and which it is the province of practicall\iechanics to teach us to combine and apply in the most advantageous numner; without which the mere command of power would amount to nothing. Practical Mechanics is, in the most pre-eminent sense, a scientific art; and it may be truly asserted, thatT almost all the great combinations of modern mechanism, and many of its refinements and nicer improvements, are creations of pure intellect, grounding its exertion upon a moderate nurriber of very elementary propositions in theoretical mechanics and geometry. On this head we might dwell long, and find ample matter, both • See a very ingenious application of this kind in l\fr. Babbage's article on Diving in the Encye. Metrop. - Others 'Will readily suggest themselves. For instance, t,he ballast in reserve of a balloon might consist of materials capable of evol",jng great quantities of hydrogen gas in proportion to their weight, should such be found.

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for reflection and wonder; but it would require not volumes merely, but libraries, to enumerate and describe the prodigies of ingenuity which have been lavished on every thing connected with machinery and engineering. By these it is that we are enabled to diffuse over the whole earth the productions of any part of it; to fill every comer of it with miracles of art and labour, in exchange for its 'peculiar commodities; and to concentrate around us, in our dwellings, apparel and utensils, the skill and workmanship not of a few expert individuals, but of all wI10, in the present and past "generations, have contributed their improvements to the processes of our manufactures. (59.) The transformations of chemistry, by which we are enabled to convert the most apparently useless materials into important objects in the arts, are opening up to us every day sources of wealth and conyenience of which former ages had no idea, and which have been pure gifts of science to man. Eyery department of art has felt their influence, and new instances are continually starting forth of the unlimited resources which this wonderful science developes in the most sterile parts of nature. Not to mention the impulse which its progress has given to a host of other sciences, which will come more particularly under consideration in another part of this discourse, what strange and unexpected results bas it not brought to light in its application to some of the most common objects! Who, for instance, would have conceived that linen rags were capable of producing more tltan their ou,"n weigllt of sugar, by the simple agency of one of the cheapest and most

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abundant acids? --tlIat dry bones could be a magazine of nutriment, capable of preservation for years, and ready to yield up their sustenance in the form best adapted to the support of life, on the application of that powerful agent, steam, which enters so largely into all our processes, or of an acid at once cheap and durable? t- that sawdust itself is susceptible of conversion into a substance. bearing no remote analogy to bread; and though certainly less palatable than that of flour, yet no way disagreeable, and both wholesome and digestible as well as highly nutritive? t What economy, in all processes where chemical agents are employed, is introduced by the exact knowledge of the proportions in which natural elements unite, and their mutual powers of displacing each other! 'Yhat periection in all the arts where fire is employed, either in its more violent applications, (as, for instance, in the smelting of metals by the introduction of well adapted fluxes, whereby we obtain the whole produce of the ore in its purest state,) or in its milder forms, as in sugarrefining (the whole modern practice of which depends on a curious and delicate remark of a late eminent scientific chemist on the nice adjustment of temperature at which the crystallization of syrup takes place); and a thousand other arts which it would be tedious to enumerate I .. The sulphuric. Bracconot, Annales de Cbimie, voL zii. p.184. t D' Arcet, Annales de I'Industrie; Fevrier, 1829. See Dr. Prout's account of the experiments of professor Autenrieth of Tubingen. Phil. Trans. 1827. p.S81. This disc.()very, which rendeN famine next to impossible, deserves a higher degree of celebrity than it has obtmoecL

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(60.) Armed with such powers and resources, it is no wonder if the enterprise of man should lead him to form and execute projects which, to one uninformed of their grounds, would seem alta. gether disproportionate. Were they to have been proposed at once, we should, no doubt, have rejected them as such: but developed, as they have been, in the slow succession of ages, they have only taught us that things regarded impossible in one generation may become easy in the next; and that the power of man over nature is limited orily by the one condition, that it must be exercised in comforrnity with the laws of nature. He must study those laws as he would the disposition of a horse he would ride, or the character of a nation he would govern; and the moment he presumes either to thwart her fundamental rules, or ventures to measure his strength with hers, he is at once rendered severely sensible of his imbecility, and meets the deserved punishment of his rashness and folly. But if, on the other hand, he will consent to use, without abusing, the resources thus abundantly placed at his disposal, and obey that he may command, there seems scarcely any conceivable limit to the degree in which the average physical condition of great masses of mankind may be improved, their wants supplied,. and their conveniences and comforts increased. Without adopting such an exaggerated view, as to assert that the meanest inhabitant of a civilized society is superior in physical condition to the lordiy savage, whose energy and uncultivated ability gives him a natural predominance over his fellow denizens of the forest,-at least, ifwe compare

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like with like, and consider the multitude of human beings who are enabled, in an advanced state of society, to subsist in a degree of comfort and abundance, which at best only a few of the most fortunate b a less civilized state could command, we shall not be at a loss to perceive the principle on which we ought to rest our estimate of the advantages of civilization; and which apI-lies with hardly less force to every degree of it, when contrasted with that next inferior,- than to the broad distinction between civilized and barbarous life in general. (61.) The difference of the degrees inwhich the individuals of a great community enjoy the good things of life has been a theme of declamation and discontent in all ages; and it is doubtless our paramount duty, in every state of society, to alleviate the pressure of the purely evil part of this distn"bution as much as possible, and, by all the means we can derise, secure the lower links in the chain of society from dragging in dishonour and wretchedness: but there is a point of view in which the picture is at least materially altered in its expression. In comparing society on i~ present immense scale, with its infant or less developed" state, we must at least take care to enlarge every feature in the. same proportion. If, on comparing the very lowest states in civilized an(1 savage life, we admit a difficulty in deciding to which the preference is due, at least in every superior grade we cannot hesitate a moment; and if we institute a similar comparison in every different stage of its progress, we cannot fail to be struck with the rapid rate of dilatation which every degree upward of the scale, so to speak, exF 2

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hibits, and whicll, in an estimate of averages, gives an immense preponderance to the present over every former condition of mankind, and, for aught we can see to the contrary, will place succeeding generations in the same degree of superior relation to the present that this holds to those passed away. Or we may put the same proposition in other words, and, admitting the existence of every inferior grade of advantage in a higher state of civilization which subsisted in the preceding, we sllall find, first, that, taking state for state, the proportional numbers of those who enjoy the higher degrees of advantage increases with a constantly accelerated rapidity as society advances; and, secondly, that the superior extremity of the scale is constantly enlarging by the addition of new degrees. The condition of a European prince is now as far superior, in the command of real comforts and conveniences, to that of one in the middle ages, as that to the condition of one of his own dependants. (62.) The advantage"s conferred by the augmentation of our physical resources through the medium of increased knowledge and improved art have this peculiar and remarkable property, - that they are in their nature diffusive, and cannot be enjoyed in any exclusive manner by a few. An eastern despot may extort the riches and monopolize the art of his subjects for his own personal use; he may spread around him an unnatural splendour and luxury, and stand in strange and preposterous contrast with the general penury and discomfort of his people; he may glitter in jewels of gold and raiment of' needlework; but the wonders of wen

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contrived and executed manufacture which we use daily, and the comforts which have been invented, tried, and improved upon by thousands, in every form of domestic convenience, and for every ordinary purpose of life, can never be enjoyed by him. To produce a state of'things in which the physical advantages of civilized life can exist in a high degree, the stimulus of increasing comforts and con8tantly elevated desires, must have been felt by millions; since it is not in the power of a few individuais to create that wide demand for useful and ingenious applications, which alone can lead to great and rapid improvements, lIDless backed by that arising from the speedy diffusion of the same advantages among the mass of mankind. (63.) If this be true of physical advantages, it applies with still greater force to intellectual. Knowledge can neither be adequately cultivated nor adequately enjoyed by a few; and although the conditions of our existence on earth may be such as to preclude an abundant supply of the physical ne-' cessities of all who may be born, there is no such law of nature in force against that of our intellectual and moral wants. Knowledge is not, like food, destroyed by use, but rather augmented and perfected. It acquires not, perhaps, a greater certainty, but at least a confirmed authority and a probable duration, by universal assent; and there is no body of knowledge so complete, but that it may acquire accession, or so free from error but that it may receive correction in passing through the minds of millions. Those who admire and love knowledge for its own sake ought to wish to see its elements made F 3

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accessible to all, were it only that they may be the more thoroughly examined into, and more effectually developed in their consequences, and receive that ductility and plastic quality wllich the pressure of minds of all descriptions, constantly moulding them to their purposes, can alone bestow. But to this end it is necessary that it should be divested, as far as possible, of artificial difficulties, and stripped of all such technicalities as tend to place it in the light of a craft and a mystery, inaccessible without a kind of apprenticeship. Science, of course, like every thing else, has its o",n peculiar terms, and, so to speak, its idioms of language; and these it would be unwise, were it even possible, to relinquish: but every thing that tends to clothe it in a strange and repulsive garb, and especially every thing that, to keep up an appearance of superiority in its professors over the rest of mankind, assumes an unnecessary guise of profundity and obscurity, should be sacrificed without mercy. Not to do this, is to deliberatelyreject the light which the natural unencumbered good sense of mankind is capable of tllfowing on every subject, even in the elucidation of principles: but where principles are to be applied to practical uses it becomes absolutely necessary; as all mankind have then an interest in their being so familiarly understood, that no mistakes shall arise in their application. (64.) The same remark applies to arts. They cannot be perfected till their whole processes are laid open, and their language simplified and rendered universally intelIigible. Art is the application of knowledge to a practical end. If the knowledge be merely

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accumulated experience, the art is empirical; but if it be experience reasoned upon and brought un der general principles, it assumes a higher character, and bec.omes a scientific. art. In the progress of mankind from barbarism to civilised life, the arts ~ecessarily precede science. The wants and cravings of our animal constitution must be satisfied; the comforts, and some of the luxuries, of life must exist. Something must be given to the vanity 01 show, and more to the pride of power: the round of baser pleasures must have been tried and found insufficient, before intellectual ones can gain a footing; and when they have obtained it, th(; delights of poetry and its sister arts still take precedence of contemplative enjoyments, and the severer pursuits of thought; and when these in time begin to charm from their novelty, and sciences begin to arise, they will at first be those of pure speculation. The mind delights to escape from the trammels which had bound it to earth, and luxuriates in its newly found powers. Hence, the abstractions of geometrythe properties of numbers - the movements of the celestial spheres - whatever is abstruse, remote, and extramundane - become the first objects of infant science. Applications come late: the arts continue slowly progressive, but their realm remains separated from that of science by a wide gulf which can only be passed by a powerful spring. They form their own language and their own co~ventions, which none but artists can understand. The whole tendency of empirical art, is to bury itself in technicalities, and to place its pride in particular short cuts and mysteries known only to adepts; to surprise and astonish F

4
a series of investigations on the chemical nature of a peculiar acid, by noticing, accidentally, a bitter taste in a • Edinburgh Phil. lourn. 1819, voL i. p. 8.

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liquid about to be thrown away. Chemistry is full of such incidents. (114.) In transient phenomena, if the number of particulars be great, and the time to observe them short, we must consult our memory before they have had time to fade, or refresh it by placing ourselves as nearly as possible in the same circumstances again; go back to the spot, for instance, and try the words of our statement by appeal to all remaining indications, &c. This is most especially necessary where we have not observed ourselves, but only collect and record the ohservations of ot.hers, particularly of illiterate or prejudiced persons, on any rare phenomenon, such a~ the passing of a great meteor, - the fall of a stone from the sky, - the shock of an earthquake, - an e~'traordinary hailstorm, &c. (115.) In all cases which admit of numeration or measurement, it is of the utmost consequence to obtain precise numerical statements, whether in the measure of time, space, or quantity of any kind. To omit this, is, in the first place, to expose ourselves 1'0 illusions o( sense which may lead to the grossest errors. Thus, in alpine countries, we are constantly deceived in heights and distances; and when we have overcome the first impression which leads us to under-estimate them, we are then hardly less apt to run into the opposite extreme. But it is not merely in preserving us from exaggerated impressions that numerical precision is desirable. It is the very soul of science; and its attainment affords the only criterion, or at least the best, of the truth of theories, and the correctness of experiments. Thus, it was

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entirely to the omission of exact numerical determinations of quantity that the mistakes and confusion of the Stahlian chemistry were attributable,a confusion which dissipated like a morning mist as soon as precision, in this respect, came to be regarded as essential. Chemistry is in the most pre-eminent degree a science of quantity; and to enumerate the discoveries which have arisen in it, from the mere determination of weigl1ts and measures, would be nearly to give a synopsis of this branch of knowledge. 'Ve need only mention the law of definite proportions, which fixes the composition of every body in nature in determinate proportional weights of its ingredients. (116.) Indeed, it is a character of all the higher laws of nature to assume the form of precise quantitative statement. Thus, the law of gravitation, the most universal truth at which hUyUan reason has yet arrived, expresses not merely the general fact of the mutual attraction of all matter; not merely the vague statement that its influence decreases as the distance increases, but the exact numerical rate at which that decrease takes place; so tbat when its amount is known at anyone distance it may be calculated exactly for any other. Thus, too, the laws of crystallography, whichTImit the forms assumed by natural substances, when left to their own inherent powers of aggregation, to precise geometrical figures, with fixed angles and proportions, have the same essential character of strict mathematical expression, without which no exact particular conclusions coilld ever be drawn from them. (117.) But, to arrive at laws of this description, it is

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