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wards contended that the earth is at the centre of the universe, compared with which, he says it is but a point; he denied the possibility of its having a movement of translation or rotation, because, he observed, all the bodies on its surface would be thrown from it into space; and it would follow, he thinks, that no cloud, bird, or projected body could advance towards the east, because it would be left behind by the superior velocity of the earth in the same direction. It is remarkable, says Mr. Narrien, that this opinion should have so long prevailed among the ancients, for it could hardly have escaped the observation that, when a ship is sailing, even with the utmost rapidity, the motion of any object thrown from the hand of a person on board is neither retarded when in the same direction 'as that of the ship’s motion, nor accelerated when in the contrary direction; and the reason is, that the original impulse is compounded of the projectile force, and that resulting from the movement of the ship, and, therefore, relatively to the ship, a projected body nioves as if the ship were at rest. The composition and resolution of motions may not have been understood in those days, but the circumstance above related must have been known; and it would be very natural to infer that the paths of bodies projected from the earth were, in
in support of his opinion of the quiescence of the earth, that it would be contrary to nature for such a heavy body as the latter to be endowed with motion, and the celestial bodies be at rest ; though he grants that a movement of rotation in the earth would facilitate the explanation of many celestial phenomena. The same philosopher, or his commentator Theon, seems to admit the existence of antipodes, for, in speaking of certain phenomena of the heavens, the latter shows how they would be modified with regard to a people so situated.
After fully explaining the planetary theory of Ptolemy, our author proceeds to investigate the labours and the success of the Arabian and Hindu astronomers, and also the cultivation of that science in China. He pursues the investigation through the middle ages, and comes at last to the era of Tycho Brahe and Kepler. The discoveries of Galileo respecting the laws by which material bodies act upon one another, shed a light upon an immense number of obscure tracks which led to astronomical information. Galileo was the individual, too, who had shown the great value of the telescope; for up to his time, none of the celestial bodies, except the sun and moon, were observed to have any visible form or magnitude. Mr. Narrien's reflections upon the benefits conferred on science by this instrument are philosophical and just. " That an instrument,” says he, “ should have been invented, by which objects, even in the remotest depths of space, are rendered accessible to human vision ; and by which terrestrial objects, faintly visible in the distance, are brought, as it were, close to the eye, must have at one time appeared miraculous; but such were the effects pro
duced by the telescope, a tube containing a system of glass lenses, in passing through which, the rays of light coming from an object, are turned from their previous directions, and made to converge towards the axis, so that the rays proceeding from opposite sides of the object, and entering the eye, form there an angle many times greater than that caused merely by the refractive powers of the eye itself, while the interference of rays coming from surrounding objects is almost wholly prevented; thus is produced an augmentation of the visible magnitude of an object, with as small a diminution as possible of its brilliancy, and thereby may be obtained a view of the parts of its surface, which would be insensible to the unassisted sight; the object being seen in the telescope, just as it would appear to a spectator without one, if situated as much nearer, as the power of the telescope exceeds that of the natural eye. This instrument, in the hands of Galileo, was the means of making more discoveries in the heavens than had been made during three thousand years previously; and it may be added, if we consider their importance, more than have been made since the days of that phi. losopher.”
But though the telescope confirmed amply the hypotheses of Copernicus and Kepler concerning the dispositions of the bodies composing the solar system, still there were individuals, men of judgment, ability, and scientific acquirements, too, who literally refused to be better informed than they were ; and it is not a little curious, that some of these philosophers endeavoured to make the world believe, that it was a species of blasphemy to look through a telescope, because, forsooth, it tended to give a different idea of natural objects to that which was universally received. In those early days, when the fetters of ignorance were but very slowly removed from the minds of men, every discoverer of a new fact or object, in any branch of science or philosophy, was too sure to take all the pains in his power to conceal it from the whole of the world besides. Sometimes the provoking inventor maliciously explained, or perhaps, more properly we should say, mystified his discovery, by pretending to give it to the world, whilst he put it forth in the form of an anagram, or some equally unintelligible symbol. We do not know if we can blame Galileo for having conformed to the customs of his time, but the truth must be told, that he employed an ana. gram for disguising his discovery of the phases of Venus and of Saturn's ring. This practice of concealment or mystery was practised alike by the Egyptian priests, the Greek philosophers, and the Druids of the north.
When we consider, however, the peculiarity of the anagram, we shall be inclined perhaps to extend some indulgence to those who employed it. The philosopher, who consigned his discovery to this mystical object, never meant that it should be taken as an attempt to communicate it to the world : he only intended to place as it were upon record, so that if any person subsequently made a
similar discovery, the anagram would be at once the medium whereby the priority must be fairly assigned.
Thegreat key, however, to astronomy, was the theory of gravitation, the glory of having discovered which, belongs entirely to our countryman Newton. Here Mr. Narrien reminds us of the very gratifying fact, how the principal nations of Europe have had their share in the honour of advancing the cause of sound philosophy, and particularly of astronomical science. “We have seen (observes the learned author) that Germany gave birth to Copernicus and Kepler ; of whom the former, with powerful arm, overthrew the barriers raised by ancient prejudices, and advanced to some distance, though with cautious steps, over the uncertain ground beyond ; while the latter, with unwearied labour, essayed every probable path, and having found the right one, proceeded along to the very gate of truth. We have seen Italy send forth Galileo, to whose piercing eye the forms of the planetary bodies stood revealed ; and France and Holland raised up their Cassinis and Huygens, to correct and extend the knowledge of the celestial movements, and open the way to the discovery of the earth's figure and the law of gravitation."
The discovery of Newton occurred during his temporary retirement from the university of Cambridge, the plague then raging in that town. Accident merely led him to believe, according to Mr. Narrien, that “ since the attractive force of the earth, by which a stone, when unsupported, descends with an accelerated motion, has less intensity on the top of a mountain than in a valley, it might extend, though with still diminished force, to the region of the moon, and might be that power by which, in conjunction with some lateral impulsive force originally given, our satellite is made to describe its particular orbit about the earth. An erroneous estimate of the magnitude of the earth prevented Newton from, immediately, discovering the identity of terrestrial gravity with that attractive force by which the moon is retained in her orbit, by leading him to the conclusion, that the latter was greater by one-sixth than it ought to have been on that supposition; but when, subsequently, on occasion of a letter from Dr. Hook, containing an enquiry into the nature of the line described by a body in falling from a great height, according to the laws of acceleration delivered by Galileo, taking also into consideration the diurnal movement of the earth, he was induced to renew, with more accurate data, his investigations concerning the action of the earth on the moon, he obtained demonstrative evidence of that identity. For, having obtained the dimensions of the moon's orbit, and the value of the arc described by that celestial body in one day, he computed the versed sine, which is a decomposed part of the motion in the arc, and found it equal to the space through which any body in that region would descend towards the earth, in the same time, by the attraction of
the latter, supposing this attraction to diminish in the inverse ratio of the square of the distance.” · A curious development of the jealousy of man characterized the discovery of Newton, as well as that already mentioned of Galileo. Although its difficulties could only be understood by a few highly educated men in Europe, still the envy and hostility against him purely as a discoverer, induced a considerable number of individuals in different countries to set themselves to work, in order to detract from the merit of that admirable philosopher. They maintained that the theory of gravity had been long known before, and thought that by establishing the truth of this assertion, they had succeeded in discomfiting the pretensions of Newton. But they had not the sense to see that his claims were of a totally different kind, and that he boasted merely of bringing before the world the knowledge of a means, whereby a certain power produces the phenomena that we now know to result from gravitation. It also happened that men perfectly impartial and well acquainted with the subject, nay, even well affected towards him, and admirers of his genius, rejected his law of the mutual attraction of material bodies, as being only a revival of the exploded doctrines of occult qualities.
The feature which chiefly distinguishes modern from ancient astronomy, is the more extensive application to this science of instruments for measuring time. " The first notice," as we are informed by Mr. Narrien, “ that is met with as to the employment of a pendulum to ascertain small portions of time, is in an account of the method by which Mouton, of Lyons, attempted to measure the diameter of the sun ; this consisted in counting the number of vibrations performed while the disc of the luminary was passing over a vertical line situated in the plane of the meridian ; the arc of the equator described by the sun, in the time of a given number of vibrations, being determined by computing the angle at the pole corresponding to that between the vertical planes passing through two plumb lines situated near the meridian, at some distance from the eye, and counting the number of vibrations performed while either limb of the sun, on the day of the equinox, was moving from one line to another. Vindelinus, Kircher, and Ricciolus, had also made use of pendulums for ascertaining the duration of phenomena; but Huygens was the first to determine what should be their length, that each vibration might be performed in one second of time."
One of the most interesting chapters in this volume is that which treats of the operations engaged in at various periods for determining the figure of the earth. The author describes the measure of an arc of the terrestrial meridian in France, in Lapland, and in various other parts of the world, together with the experiments of Captain Sabine on the lengths of the pendulum.
Mr. Narrien, in reviewing the latest discoveries in astronomical science, attributes the addition of many facts relating to the con
stitution of the bodies composing our system to the highly improved state of the instruments which are employed in modern astronomy for the purpose of observations of the heavens. Thus it was entirely owing to the unparalleled superiority of his telescopes, that he was able to examine so minutely the spots on the sun, as to justify him in attempting to determine their origin. His opinion of this phenomenon is well known to be as follows :-" That these spots are produced by an elastic gas, which, issuing from the solid matter composing the body of the sun, piercing the luminous strata surrounding it, and dispersing itself every way about the orifice, permits the dark nucleus at the bottom of the perforation to become visible to a spectator on the earth, when the latter is in the direction in which the perforation has been made; at times, also, Sir William was able to look obliquely down the opening, and distinguish, by a difference of colour, on the side opposite to the eye, the direction of the thickness of the luminous mass. The elasticity of the gas appears, frequently, insufficient to allow the particles to make their way through the matter which surrounds the sun, and then it swells it into ridges or nodules, appearing more brilliant than the rest of the surface; or, escaping in small quantities, it disturbs the upper surface only, causing gentle swellings or shallow indentations; the last of which are rather more obscure than the other parts of the sun, and contain many small dark points, like pores, through which some of the ascending gas has passed.”
Upon a purely technical subject such as this, we cannot be very lavish of space. We are, however, aware that much injustice may appear to be done to a work of great importance when it obtains a contracted notice : but those who would object that we have devoted too few of our pages to this question, as well as those who may be of opinion that we have granted too much, will only do us justice by giving us credit for a desire to attain the golden mean, that is to say, to do justice to the merits of the author, but at the same time to consult the inclinations of the reader. This work, it will be easily seen, possesses all the qualities which could be combined in it by one who is evidently gifted with the highest intellectual endowments.
Art. XIV.-Sketches of Canada and the United States. By WM. L. MacKenzie. 1 vol. thick 8vo. London: Wilson. 1833.
We consider this to be a very useful book in this country, inasmuch as it more faithfully pourtrays, than any production lately issued on America which we have seen, the actual condition of the society of the middle and humbler classes in that country, and particularly in Canada. The writer emigrated to the latter place, and has been