so that the voyager finds he can trust to his chart and compass alone, without constantly looking out, or having the sounding line perpetually in his hand.

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It has, moreover, been observed of Bacon, that he placed the ultimate object of philosophy much too high. He seems to have thought that by efforts skilfully and perseveringly directed, the student of nature might arrive at the knowledge not only of the qualities and powers which belong to things, but of the essences themselves of these qualities and powers that he might, for instance, become acquainted with the essence of heat, of cold, of colour, of transparency. His lordship pursued this idea still farther; for, assuming the possibility of discovering the essence of qualities, or that particular constitution of any set of substances whence their qualities arise, he imagined that by imitating that arrangement of parts in other substances, or, to use his own language, by inducing on any other set of bodies the form of the qualities which belonged to those in which the discovery was made, the same qualities might also be induced on the bodies in question. For example, having succeeded in finding out the forms of the yellow colour, the specific gravity, and of the other qualities of gold; the philosopher, according to the views of Bacon, would be able to induce these forms on iron, and give it, of course, all the properties of gold. In a word, the scientific dreams of the great reformer of learning, were suggested by the magnificent but very foolish projects of the alchemists, whose absurdities he labours so sedulously to expose: whence it appears that, in his strictures on the conduct of those ingenious men, he condemned the means rather than the end, and whilst he deplored their want of success, he seems never to have regarded their object either as unphilosophical or unattainable.

"It was natural," says Mr. Playfair, "that Bacon, who studied these subjects theoretically, and saw nowhere any practical result in which he could confide, should listen to the inspirations of his own genius, and ascribe to philosophy a perfection which it may be destined never to attain. He knew from what it had not yet done, he could conclude nothing against what it might not accomplish hereafter. But after his method has been followed, as it has now been, with greater or less accuracy, for more than two hundred years, circumstances are greatly changed; and the impediments which, during all that time, have not yielded in the least to any effort, are perhaps never likely to be removed. This may, however, be a rash inference; Bacon, after all, may be in the right; and we may be judging under the influence of the vulgar prejudice which has convinced men, in every age, that they had

nearly reached the farthest verge of human knowledge. This must be left for the decision of posterity; and we should rejoice to think that judgment will hereafter be given against the opinion which at this moment appears most probable.”

The third section of the first part, to which we now proceed, is occupied with a review of the history of Mechanics, prior to the time of Newton.

In this branch of physical science the ancients have left very few written documents to mark their proficiency: and were it not that the immense architectural labours which still adorn Egypt and Greece, prove to us that their practical apparatus must have been of the first order, and constructed, of course, on the principles of a highly improved science, we should have had just cause to suspect that their knowledge of dynamics and of the laws of motion was not more than elementary. If mechanical philosophy was indeed known to the ancients, it was undoubtedly lost among the wrecks of human learning, which accompanied the downfal of their political establishment; for we find that on the revival of letters in Europe, the few mathematical scholars who have left any works, occupied themselves with enquiries, and aimed at discoveries. which sufficiently make known the low condition of all the geometrical sciences. Before the end of the sixteenth century the student of mechanics had never gone beyond the problems which treat of the equilibrium of bodies, and had been able to resolve these accurately only in the cases which can be easily reduced to the lever. It is to Galileo, that distinguished astronomer, the world owes the first great improvements in mechanical science. Like his illustrious follower, the immortal Newton, he directed his attention to the most simple phenomena of nature, and thence ascended by safe and gradual steps to the sublimest views and the most splendid generalizations. While pursuing his studies at Pisa he began, to make experiments on the descent of falling bodies, and in the course of these discovered the fact, that heavy and light bodies fall to the ground from the same height, in the same time, or in times so nearly the same that the difference can only be ascribed to the resistance of the air. From observing, too, the vibrations of the lamps in the cathedral, he, in like manner, arrived at this very important conclusion in mechanics, that the great and the small vibrations of the same pendulum are performed in the same time, and that this depends only on the length of the pendulum. These observations were made as far back as the year 1583. These experiments, we are assured, drew upon him the

displeasure of his masters, who considered it as unbecoming in their pupil to seek for truth in the book of nature rather than in the writings of Aristotle, elucidated by their commentaries; and from that moment these philosophers began the persecutions with which the prejudice, the jealousy, and bigotry of his contemporaries never ceased, during the remainder of his life, to harass and afflict this distinguished

man.

"One forms, however, a very imperfect idea of this philosopher, from considering the discoveries and inventions, numerous and splendid as they are, of which he was the undisputed author. It is by following his reasonings, and by pursuing the train of his thoughts in his own elegant though somewhat diffuse exposition of them, that we become acquainted with the fertility of his genius, with the sagacity, penetration, and comprehensiveness of his mind. The service which he rendered to real knowledge is to be estimated not only from the truths which he discovered, but from the errors which he detected; not merely from the sound principles which he established, but from the pernicious idols which he overthrew. His acuteness was strongly displayed in the address with which he exposed the errors of his adversaries, and refuted their opinions, by comparing one part of them with another, and proving their extreme inconsistency. Of all the writers who have lived in an age which was yet only emerging from ignorance and barbarism, Galileo has most entirely the tone of true philosophy, and is most free from any contamination of the times, in taste, sentiment, and opinion."

The services of Descartes, in the same line of enquiry,' are deserving of no small degree of praise, though the prineiples on which he prosecuted his discoveries were by no means equally philosophical with those of the ingenious person just named. Huygens and Hooke, too, deserve a place in the archives of mechanical science, as well for the general principles which they both so successfully illustrated, as for their very important improvements in the structure of timekeepers. The works of these gifted individuals are, however, sufficiently well known, and require not that we should enter into details to set forth their merits.

At the era of which we are now speaking several new lights were obtained on the subject of fluids, whether at rest or in motion; and the most considerable of these are due to the talents and industry of Torricelli, the friend and disciple of Galileo. The latter had expended much thought on the fact, so long observed, that water cannot be raised in a pump more than thirty-three feet, but he had never attained to the knowledge of the physical reason on which it is

founded. Torricelli, who had entered on the same investigations, fortunately thought of employing a heavier fluid than water; concluding justly that a vacuum, if such it should be called, might be produced by a much shorter and - less cumbrous method. He tried mercury, and succeeded. The result is known to every one; the suspension of the metal was ascribed to the pressure of the atmosphere-an opinion which was confirmed by carrying the instrument to the top of a mountain-and thenceforth the barometer was added to the number of philosophical inventions.

It is said that Torricelli, who venerated Galileo, was sincerely grieved that the discovery now mentioned did not present itself to the latter; a token of generosity much more rare among men than the genius which invents, or the sagacity which conjectures.

It was this discovery, as every one knows, that first demolished the formidable idol of a vacuum, to which so much power had been long attributed, and before which even Galileo, and the most enlightened of his contemporaries, had condescended to bow. The air-pump, invented by Otto Guericke, rewarded soon after the event just described, the learned industry of that distinguished burgomaster. In order to obtain a space entirely void of air, he filled a barrel with water; and having closed the vessel carefully on all sides, proceeded to draw out the fluid by means of a sucking-pump applied to the lower part of it. The result in this case, too, is familar to every scientific reader. As the water was diminished the atmosphere increased its pressure on the exterior of the barrel, and at length to such a degree that the air bursting into it with a loud noise, afforded the most direct and palpable proof imaginable of its great weight, as well as of the law by which it acts. After experiencing repeated failures, Guericke bethought himself of using a sphere of glass instead of a cask-a substitute which completely succeeded, and enabled the ingenious projector to realize his object, in the obtainment of an actual vacuum,

The elegant instrument of which we have now described the origin, owed afterwards its greatest improvements to the modest and virtuous Boyle. He not only enlarged the apparatus, but encreased the facility of using it, for the purposes of experimenting; in the practical part of which he showed a dexterity and skill which have not been surpassed, even in the laboratory of the Royal Institution. He had, indeed, as Mr. Playfair reminds us, very early applied himself to the prosecution of experimental science, and was one of the members of the small but distinguished body who, during

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the civil wars, held private meetings for cultivating natural knowledge, on the plan of Bacon. They first met in London, as early as 1645, afterwards at Oxford, taking the name of the Philosophical College: and when Charles the Second ascended the throne he granted letters patent, by which, in 1662, they were incorporated into the Royal Society of London.

There yet remain two important branches of science, of which the history, prior to the era of Newton, is given at some length by Professor Playfair, we mean astronomy and optics. On these, however, we must abstain from entering at present, because to exhibit even the most meagre outline of them would lead to an extension of this article much beyond the limits to which it was meant to be confined. In our next Number, we shall, perhaps, resume the subject, and bring down the narrative, on the small scale to which we have restricted ourselves, to the commencement of what the author calls," the period of Euler and D'Alembert."

ART. III. Belshazzar; a Dramatic Poem. By the Rev. H. H. Milman, Professor of Poetry in the University of Oxford. 8vo. pp. 166. 8s. 6d. Murray. 1822.

WE suppose it is from a natural reluctance that a deserved favourite should hazard the forfeiture of any particle of his distinguished reputation, or that he who has climbed higher on the dangerous steeps of Parnassus than any of his contemporaries, should by an over-hasty leap slide down again to the level of those whom he has o'ertopped, that we felt no pleasure when we first perceived the announcement of Mr. Milman's Belshazzar. It trod too closely on the heels of another of his Poems to permit us to hope that it had been held under the scrutinizing custody of a critical eye for more days. than Horace requires years: and we were too jealous of Mr. Milman's fame to allow, if we could help it, the suspicious number nine to approach near any of his wonders. In his. introduction, however, he has successfully removed the only objection which we could raise to the fecundity of his muse, by stating that the publication of the Martyr of Antioch was considerably delayed by unforeseen accidents; thereby implying (as we take it for granted) that Belshazzar was in great part written before this former Poem appeared. Mr. Milman