ther a light or heavy body fell fastest was a question on which no one then living had any just opinion, and on which no experiment had up to that time been perhaps, ever made. The most preposterous opinions were entertained about the path of projectiles in the air; no microscope, telescope, barometer, or thermometer, had been heard of. The laws of simple refraction were unknown. Natural philosophy existed only in the form of a rude and inaccurate mechanical astronomy, a few useless optical and pneumatical toys, and a great mass of dogmatic theories as to principles which ought (if they did not) to regulate the course of nature. Thus things were towards the middle of the sixteenth century.

TWO HUNDRED YEARS SINCE, Newton was a boy at school. The mere ground plan of the solar system was pretty well understood, but gravitation was unthought of, or was, at least, a mere surmise. With the exception of Jupiter's satellites, the received number of the heavenly bodies was then the same as the ancients had acknowledged. The true figure of the earth was unrecognized. The Principia and the Optics of Newton were, of course, unwritten. The compound nature of light and its progressive motion were unknown: only one law had been added to optics since the time of Ptolemy. The air-pump had yet to be made; and the astonishing power of the hydraulic press was still a secret. Electricity and magnetism had hardly even a name as sciences. Pure mathematics was still deficient in one great organ of modern research-the differential calculus.

ONE CENTURY AGO, or in 1757, Watt had not dreamt of his steam-engine; the laws of heat were almost absolutely unknown. The electricity obtained by rubbing glass or sealing wax had begun to have several of its properties investigated, but comparatively little progress had then been made. The astonishing powers of galvanism were as yet utterly unsuspected. Chemistry was but a name, scarcely even that. Water was regarded as a simple substance, and the variety of the gases was unthought of. With the single exception of the achromatic telescope, the science of optics was where Newton left it in the previous century. The interference and polarization of light were unknown terms. The partial recognition of the latter property by Huyghens had been completely lost sight of. The con

nection of magnetism with electricity was yet to be hidden for sixty years; and the inventions of the electric telegraph, the locomotive engine, and the railway, were to be witnessed by the grandchildren and great-grandchildren of these entering upon life. The earliest known of periodic comets had not then by its return verified the sagacious prediction of Halley. The Herschel planet was yet to be added to the catalogue of our solar system: much more that mysterious star whose existence was foreshadowed and its discovery rendered possible by the irregularities of the motion of the former. The interminable list of asteroids between Mars and Jupiter had not then commenced. Our own globe had not yet been weighed as in a balance, and sun had not been seen to encircle sun in a mutual orbit connecting the law of gravity with those awful depths of space.

This brief and partial enumeration of scientific discoveries may serve to give us a feeble insight into the general position of natural knowledge at periods not remote from our own in comparison with the duration of our species, or even of the historic period. When we attempt to comprehend at a glance what have been the general laws of progress during these latter ages, we may find, notwithstanding the extent and variety of the subject, some recognizable features which distinguish their subdivisions. If we divide the centuries by their middle instead of at their termination, we shall find these features more clearly brought out. And though, as we have shown, the science of three hundred years back, or of 1550, seems now to us one of almost infantile imbecility, and therefore a fit startingpoint of progress, we may as well include a period still a century more remote, which embraces almost the earliest efforts towards philosophical regeneration, and also the memorable invention of printing, which contributed incalculably to intellectual progress of every kind.

Thus our scheme of modern scientific chronology embraces four centenary periods. The first, from 1450 to 1550, which was characterized by the appearance of Leonardo da Vinci and Copernicus, may be termed Preludial or Anticipatory. It was marked rather by the attempt to proceed in a right direction, and to attain a right method in learning the truths of nature, than by extensive or signal success

in this investigation. We might compare those efforts to the gleams of light which gladden the view of the imprisoned Arctic navigator when the sun promises once more to revisit the melancholy realms of Polar frost. They tell as much of the thick darkness which is about to be dissipated as of the bright day of which they are the herald. Or, to adapt the metaphor to our own climate, the early struggles of the human intellect to disperse the obscurity and to awaken the death-like unconcern of the middle ages, resemble those first bright days at the transition from winter to spring, when we welcome the feeble sunbeam as a sure earnest of its coming power.

The next age, (1550-1650,) which was that of Kepler, Galileo, and Bacon, may be emphatically called the age of Progress. The clear convictions then attained as to how science could best be promoted, and as to the errors which had hitherto obstructed its career, and also the complete success which attended the application of this, the inductive method, to great questions of mechanics and astronomy, allow us, without hyperbole, to compare it to the advent of spring-cheering, warming, and enlightening; a time of emphatic transition from one condition of thinking and acting to another; a period of fulfillment; yet even more, a period of glorious promise. The sun fairly mounted high above the horizon, seems to triumph over darkness, "shining more and more unto the perfect day." The forests are rapidly becoming clothed with foliage, the meadows with verdure; a genial sap fills all organic nature, and intense Life manifests itself at every pore.

The third centenary of our history (1650-1750,) or that of Newton, was emphatically the age of Attainment. Let us think of ourselves as well as we please, let us praise the enlightenment of the nineteenth century, the diffusion of education, the abatement of prejudices, and the astonishing triumphs of art- -- no one whose opinion is worth having, hopes or expects that our age will eclipse that in which the Principia first appeared. It may be not inaptly likened to the early weeks of glorious summer, when the mighty sun, approaching the solstice, shines on a world still fresh in all the beauty and radiance of spring, whose verdure is unsoiled, and whose fairest flowers are now expanded. All nature seems to rejoice in

having thus triumphantly put forth her hidden strength. The truths of science are now no matters of speculation but of certainty, and being set in the open face of day, are capable of being seen and admired by all men.

The fourth or modern age, extending from 1750 to 1850, we would by no means qualify as a period of decline; yet neither dare we assert that it is brighter or more admirable than that which preceded it. The glorious sun can not rise higher than it is at the Tropic, but in the sphere of intellect it may pause there, and not hasten its going down. Still, the character of the epoch may and must change. Time and events never pause, but still leave their traces. The sky is perhaps less serene than before, the heat is more scorching; the freshness of the springtime and early summer is gone. The harvest is every where, the laborers by comparison few. Tender shoots have now become vigorous stems; the fair flowers which decorated the orchards have become golden fruit which weighs down the branches. The burden and heat of the day falls on the laborers of the fourth age. It is the season of Enlargement and Application. Now we are to learn to use wisely and discreetly the teachings of the past. Gross errors have been removed from our path. Other entanglements arise-less palpable, less positive, yet not always therefore easier to overcome. Our time has also its les

sons and its warnings.

And now, to drop metaphor, let us look more closely into what may be these lessons and warnings. We may be sure that they have an application for all. While we are inquiring why some men failed formerly to know what they might have known, and why others now attain. knowledge without at the same time attaining wisdom, or the great end of knowledge, we discover something which may be turned to account, not only by the few who engage in the noble task of enlarging science and demonstrating new laws of nature, but by the many who are interested in learning what these laws are, and how they may best be employed for the benefit of humanity.

It is a common mistake to pride ourselves upon our immunity from those errors or vices to which we are by circumstances or temperament least prone. In like manner it is easy to dwell with com

Of the erroneous modes of thought which enthralled the speculative minds of the fifteenth and sixteenth centuries, two were conspicuous: first, an overstrained and excessive regard to the opinions held by the ancients; and secondly, an underestimate, and indeed a total misapprehension, of the value of experiment, and the manner of applying it so as to give useful results. Both of these defects may be traced to a certain inactivity of mind which rendered inquiry a tedious and repulsive task. It was easier to adopt unquestioned the opinions of Aristotle than to investigate their truth. It was easier to insist that the beauty and simplicity of a circular curve fitted it alone for the celestial motions, than to search out with patience the actual form of the planetary orbits. Nay, in the temper of those times, it was pleasanter and easier to demonstrate upon paper that a body ten pounds in weight must by the nature of things fall ten times as far in a minute as a body weighing one pound, than to ascend with Galileo the leaning tower of Pisa, and, allowing two weights to drop, to bear testimony to the result. Even the patience of the alchemist was a kind of vis inertia. Experiments, indeed, they made without number, but without the exercise of that vitality of thought which alone renders experiment fruitful. One thing only they saw clearly, and that was the Result, which they desired to attain. The reasonable connection of the means and the end was overlooked. Experiment is an unavailing mockery if it is used only to support a foregone conclusion.

It was a real revolution, not only in methods of inquiry, but in the temper with which men approached the unknown questions of natural philosophy, which characterized these ages of Revival and Progress. He who could create or destroy a law of nature by a stroke of the

and compass, was little likely to tease himself by the interpretation of experiments, or to disturb his rest by patiently watching the courses of the stars. The caution of Galileo and the endurance of Kepler were, no doubt, bywords among the maintainers of the older views; but it is from their time that we date that attention to scrupulosity of observation which is the very keystone of the inductive philosophy.

Henceforward it was no longer the prerogative of genius to attend only to great things, and to let the little things take care of themselves. The theory of the universe turned, upon more than one occasion, upon attention to what might be called minutiae. Thus when the Ptolemaic theory (which accounted for the apparent irregularities of the planetary motions by the hypothesis of Epicycles) was at length found to be unequal to representing accurately the orbit of Mars, the discrepancy was small considering the state of the astronomy of those days. It amounted to only eight minutes of a degree. But great or small, no one could gainsay the error of the theory. Kepler, with a spirit worthy of Newton, declared that out of these 8' he would construct a new astronomy: and he did so. The discovery of elliptic orbits, and that of the equable description of Areas (two of the corner-stones of the modern astronomical edifice) were the result. Some years later, Newton made a similar concession to the unbending requirements of truth. In order to show that the fall of a stone may be due to the very same force residing in the earth, which, modified by the proportion of the inverse square of the distance, draws the moon from a rectilinear course into an orbit approximately circular, it was necessary to know the dimensions of our earth in miles or feet. Newton, assuming the rude measure of a degree then in common use, making it equal to sixty English miles, obtained a result differing about one eighth part from that which his theory ought to have given. The theory, though not forgotten, was abandoned for a time, and only after eighteen or nineteen years' delay was it resumed, when a more accurate measure of our globe had come to his knowledge. We almost tremble to think what might have been the result had Newton died during this long pause, and had the Prin

cipia consequently never been written. We are almost tempted to say that the genius of the new philosophy was too exacting, that the caution of her votaries had run to an excess in a direction opposite to the mistakes of the schoolmen.

But it is not so. The uncompromising lesson of cautious induction which Newton thus practically taught, was better worth knowing than even the law of gravity. The result has been that this lesson, now nearly two hundred years old, has never been forgotten. It will continue to be quoted for the instruction of students for ages yet to come, in proof of the rigor which belongs to the right interpretation of nature.

And now, turning from the earlier to the latest age of modern science, from the sixteenth and seventeenth to the nineteenth century, have we become so wise as to have exploded error by our mode of arriving at truth? Have our successes borne a due proportion to our teaching and experience?

If, as has been already remarked, the opposite of error be necessarily truth, and that of failure, success, our own age has nothing to fear from a comparison with the ages of Copernicus and Galileo. We shall hardly be suspected of an excessive addiction to authority, to empty logical distinctions, nor of an antipathy to experimental methods. These of course are not the weak points of the philosophy of our time. They may more properly be thought to consist in an extreme opposition to the errors of our forefathers producing contrary defects. A passion for originality, an undue depreciation of the merits of those who have preceded us, and an exaltation of slight improvements into substantive discoveries, are common enough examples of this. But we shall better understand the tendencies of the science of our time if we observe the twofold direction of its expansion. The one results from the numerous mechanical applications of science, the other from its theoretical refinements. The one tends to induce an unreasoning wonder at inordinate exertions of mere brute force, the other expatiates in subtle mathematical refinements. The one places its glory in the dominion of man over the stubborn conditions of matter; the other diverts a different class of minds from the more fruitful theories of natural philosophy into

the region of abstractions whose applications remain dubious, or into the still more debatable land conterminous between metaphysics and physics.

It

As regards the former or mechanical side of modern science, it must be owned that the public generally are but indifferent judges as to the inventions or the men most worthy of applause and imitation. We do not mean that the calm verdict of an after generation is thus usually in error, but rather that of lookers-on whilst social improvements based on scientific discoveries are in progress. The great inventions of James Watt and of George Stephenson were only accepted after innumerable prejudices were overcome. is rather a matter of surprise than otherwise that those distinguished and modest engineers ever reaped a substantial reward for their eminent services. We find that their improvements were assailed not only with detraction, but by every form of legal and Parliamentary opposition, and in a few instances even by chicanery and violence. But the confidence thus withheld from the originators of the steamengine and the railway, has by a natural revulsion of popular feeling been often bestowed on imitators who, knowing how to avail themselves of the tide of opinion, endeavor to throw their achievements into the shade by carrying out their principles to greater and often extravagant lengths. Be it ever recollected, that merely mechanical ingenuity is one of the commonest endowments. In the sixteenth century it developed itself in schemes often absurd and impracticable, almost always speculative and untried. The stock inventions of the nineteenth (when this doubtful kind of science has almost degenerated into a trade) are frequently, indeed, foolish and baseless mechanical projects, but still oftener they are merely simple deductions from known principles inflated into temporary importance by the ingenuity of fortune-hunters. Such applications of science begin and end within themselves. They lead to no ulterior progress, because they contain no vital spirit.*

*Our remarks are confirmed and illustrated whilst

penning these sentences by a recent correspondent in the Times on the "Alleged Discovery of the Mechanical Utility of Electro-magnetic Engines." A competent authority, Mr. Joule, of Manchester, writproposed scheme, concludes with an observation ing in that journal to demonstrate the fallacies of the which is applicable to a majority of similar projects. "It is humiliating to see how readily the matured

The error opposite to this is to be found in refinements of theory, either trifling in themselves or destitute of a practical bearing, or else fallacious, because founded on insufficient data. Of course it is impossible to rate too highly the importance of a knowledge of theoretical mechanics, and of the highly complex mathematical artifices by which it may be applied to explain the laws of nature as in physical astronomy, or to anticipate the working of artificial arrangements as in ship-building, in the construction of tubular bridges, or in the performance of a clock or a steamengine. But it is also possible to spend a lifetime in the solution of problems which can scarcely be more than curious amusements. Indeed, it is the mistaken idea that much of the time of mathematicians and natural philosophers is spent in such "curious trifling," which often raises a sneer at their expense on the part of persons who are little acquainted with the eminently practical nature of the problems which science resolves. It is indeed (as Bacon maintained) an eminent criterion of our being well employed, that our labor shall not terminate in itself, but be fruitful-fruitful of knowledge, or fruitful of applications. The solution of curious or highly abstract problems, though to a limited extent a commendable exercise, is ever to be guarded against when it is valued on its own account as a dexterous achievement. In this respect it ranks with the dexterity of the chess-player, and no higher.

In confirmation of this remark it may be observed that the ablest mathematicians, though they have often commenced their career amidst the most abstruse and inapplicable generalizations of the science of quantity, have, with few exceptions, gradually descended, (as some might call it,) or as we ought rather to say ascended, to the consideration of definite, concrete, and practical questions, than which none afford more scope to the most enterprising student or analyst. Farther, in cases where the abuse of which we speak has obtained amongst modern writers, of making to use a homely phrase-the facts of nature mere pegs on which to suspend festoons of algebraic drapery, the judgment of an eminent cultivator of science is set aside. Personally he can well afford it, knowing that truth will ultimately triumph; but he regrets deeply when he sees talent and energy misdirected through ignorance of established scientific principles."

evil may be said to extend beyond the region of trifling, for the theorist commonly falls into positive mistake. Sound mathematics lead to false results if applied to insufficient or wrongly assumed data, and the general public is misled by an array of proof altogether fallacious and delusive. It would not be difficult to cite even illustrious examples of such errors. These "follies of the wise" might figure in a chapter of the Curiosities of Literature, and are really as valueless and pernicious as the attempts of illiterate mechanics to draw from a machine an unfailing flow of power, or to obtain in the processes of manufacture results incompatible with the known laws of heat, electricity, and chemistry. That the subtle and intricate forces of nature such as those which we have just named should be misunderstood and misapplied, is inevitable in an age when the real powers of science are so amazing that the mere strangeness or seeming improbability of a result is by no means a test of its being erroneous or the reverse. The mass of mankind-who in this particular instance are nearly as prone as in the days of Galileo to swear by the authority of some celebrity, or to be attracted by the splendor of profitable promises, or to prostrate their reason and common-sense before an array of geometric symbols wholly unintelligible to them-are but too ready to applaud and to propagate the mistake.

If we now resume the inquiries: Have we become so wise as to have exploded error by our mode of arriving at truth? Have our successes borne a due proportion to our teaching and experience? the answer to the latter question, at least, must depend upon another one, namely, whether the Art of Discovery is capable of being reduced to rule? One very great man, at all events, thought that it was. Francis Bacon devoted the most celebrated and important of his writings to define and explode the errors by which the increase of knowledge was in his time retarded, and to systematize a positive method of discovery. In the former part of his task he was, to a great extent, successful; in the latter his failure was conspicuous. Not only did he himself not succeed in any model investigation, but the procedure which he recommended was not followed by any succeeding natural philosopher. Looking, however, rather to the historical evidence which now occupies us than to