It is then that "the habitually tranquil limit between the opposite up- | in Europe and America. Wealth may well per and under currents,, the upper, of course, to a be coveted when we find it thus judiciously greater extent than the lower-thus wholly or employed when in the possession of genius, partially denuding the opaque surface of the sun and thus liberally expended, when belonging below. Such processes cannot be unaccompanied with vorticose motions, which, left to themselves, to rank and station. die away by degreees, and dissipate; with this fruit of wisdom is better than gold, and her peculiarity, that their lower portions come to rest revenue than choice silver," and that they more speedily than their upper, by reason of the "who love wisdom shall inherit substance, greater resistance below, as well as the remoteness and have their treasures filled." from the point of action, which lies in a higher region, so that their centre (as seen in our waterspouts, which are nothing but small tornadoes) appears to retreat upwards. Now, this agrees perfectly with what is observed during the obliteration of the solar spots, which appear as if filled in by the collapse of their sides, the penumbra closing in upon the spot, and disappearing after it." Since the work of Sir John Herschel was drawn up, Astronomy has been making rapid advances in Europe; and as an opportunity may not soon occur of resuming the consideration of the subject, we shall now give a brief notice of some of the most remarkable results which have been obtained, and which have very recently been publishWe have been much disappointed at find- ed by M. Struve of Pulkova, in his Etudes ing that Sir John Herschel either has not ob- d'Astronomie Stellaire. This interesting served or has not described the extraordi- work, to which we have already had occanary structure of the fully luminous disc of sion to refer, is, we believe, in the possesthe sun, as we and others have repeatedly sion only of M. Struve's private friends. It seen it through Sir James South's great is drawn up as a Report, addressed to His Achromatic; a structure which should Excellency M. Le Comte Ouvaroff, Minishave been more distinctly seen at the Cape ter of Public Instruction, and President of than in our climate. This structure of which, the Imperial Academy of Sciences at St. if we recollect rightly, we have seen a beauti-Petersburg, and has the subsidiary title of ful drawing made by Mr. Gwilt, resembles Sur la Voie Lactée, et Sur les Distances compressed curd, or white Almond soap, or des Etoiles Fixes. a mass of asbestos fibres lying in a quaquaversus direction, and compressed into a solid mass. There can be no illusion in this phenomenon :-it is seen by every person with good vision, and on every part of the sun's luminous surface or envelope; and we think affords an ocular demonstration that that surface or envelope is not a flame, but a soft solid, or thick fluid maintained in an incandescent state by subjacent heat, and capable of being disturbed by differences of temperature, and broken up as we see it when the sun is covered with spots or openings in the luminous matter. After some historical notices of the speculations of Galileo, Kepler, Huygens, Kant, Lambert, and Michel, M. Struve gives a general view of the discoveries of Sir. W. Herschel on the construction of the heavens, and of his peculiar views respecting the Milky Way. He compares his opinion on this subject, as maintained in 1785, with that to which he was subsequently led, and arrives at the conclusion, which we have already had occasion to mention, that, according to Sir W. Herschel himself, the visible extent of the Milky Way increases with the penetrating power of the telescopes Such is a brief and very imperfect analy-employed; that it is impossible to discover sis of a work which exhibits in a high degree the patience and the genius of its author-a work which had he done nothing else would have given immortality to his name. Whether we view it as an indepen-him to extend our knowledge of the Milky dent production, or as the completion of the labors of his distinguished parent, it is a work truly national, to which however, the nation has contributed nothing. To the liberality and devotion to science of one individual we owe the valuable results which | it records, and to the munificence of another its publication in a separate form, and its gratuitous presentation to the Universities, the Societies, and the principal philosophers by his instruments the termination of the Milky Way (as an independent cluster of stars); and that even his gigantic telescope of forty feet focal length, does not enable Way, which is incapable of being sounded. In his next section, on the "Progress of Stellar Astronomy since the time of Herschel," he gives an account of the labors of M. Argelander, in establishing beyond a doubt the translation of our Sun, with its planets in absolute space, and those of his own son, M. O. Struve, in ascertaining the angular velocity of its motion, and in verifying the direction in which it moves, as determined by Argelander. He gives an Hours of R. Stars from 1st to Hours of R. Stars from 1st to 9th Magnitude. Ascension. I. 1516 XIII. 1533 account of the researches of Bessel, on the proper motions of Sirius and Procyon, from which that distinguished astronomer inferred the existence of large opaque bodies round which these motions are performed, and he mentions, without giving it any countenance, the bold speculation of M. Mædler of Dorpat, that the Pleiades forms the central group of the system of the Milky Way, and that Alcyone, the brightest star of the Pleiades, may be regarded as the central sun of the Milky Way, round which all the stars move with the same mean angular velocity, whatever be the inclination of their orbit, and their lineal distance from the central body. Passing over his notice of the labors of the Russian astronomers, of Sir John Herschel, and Mr. Dunlop, on the subject of nebulæ and double stars, he treats of the structure of the Milky Way, as deduced from the catalogues of Weisse, Argelander, Piazzi, and Bessel. With this view he inquires into the arrangement of the stars in the equatorial zone or belt, 30° wide, extending to 15° N. and 15° S. of the equator. In the catalogue of Weisse, there are in that belt 31,085 stars, which are divided as follows: 664 2500 8183 19738 But though only these 31,085 stars were observed by Bessel, yet M. Struve has shown, by an ingenious calculation, that there are 52,199 existing in the equatorial zone. M. Struve had shown in 1827, that if we divide the celestial vault visible in Europe by circles parallel to the equator, the stars are almost uniformly distributed in the zones thus formed, if we include at once all the 24 hours of R. Ascension; but that a very variable condensation takes place in each zone in the successive hours of R. Ascension. This will appear from the following table, showing the number of stars existing in the equatorial belt from the 1st to the 9th magnitude for each hour of R. Ascension: XII. Hence, dividing the whole zone into six regions, of four hours each, two of these are rich in stars, and four poor, the two rich regions being from V. to VIII. and from XVII. to XX.; and hence, M. Struve concludes, from a closer inspection of the table, that there is a gradual condensation of the stars towards a principal line, which is a diameter of the equatorial zone situated between the points V1h 40m and XVIII 40 of the disc. The line of least condensation is situated between the points 1h 30' and XIII 30', making an angle of 78° with the line of greatest condensation. If we divide the disc or zone into six circles parallel to the principal diameter, the density in successive bands diminishes on both sides with the distance. The line of greatest condensation does not pass through the sun. The distance of the sun from the principal diameter is about 0 15 a,* which is nearly equal to the radius of the sphere which separates the stars of the first from those of the second magnitude. The line of greatest condensation is not quite a straight line, but presents extraordinary lacunæ, as in Serpentarius, and accumulations, as in Orion. Hence the angle. of 78° between the lines of greatest and least density is explained by these anomalies, for it would otherwise have been 90°. Comparing this description of the state of the stars in the equatorial zone which encircles the sun, with the phenomena of the Milky Way, M. Struve arrives at the conof the clusion, "that the phenomenon condensation of the stars toward a principal line of the equatorial zone is closely connected with the nature of the Milky Way, or rather that this condensation and the aspect of the Milky Way are identical phenomena. The letter a denotes the radius of a sphere including all the stars seen by the naked eye. In extending this inquiry to the six million nearly (5,819,100) of stars visible in the twenty-feet telescope of Sir W. Herschel, M. Struve finds that the greatest and least densities fall very nearly on the same points of the periphery of the disc, as in the case of stars of the 9th magnitude; and he gives the following distribution of these stars in every four hours of R. Ascension: From Ih to Vh of R. Ascension, 391,700 stars. V IX XIII XIII XVII XVII XXI XXI The agreement between the radii in the gression, with the ratio From Oh to XXII 60'of R. Ascension, 581,900 stars. We regret that our narrow limits will not permit us to give a full account of M. Struve's latest researches on the Milky Way, in which he determines the law of the condensation of the stars towards a principal plane. After ascertaining that the number of stars in the whole celestial sphere, as seen by Sir W. Herschel's twenty feet telescope, amount to (20,374,034) upwards of twenty millions, he obtains the following values of the density of the stars, and of the 6 A 6.2093 7.7258 8.8726 6 B .. 8.2161 7 B 8.2160 14.4365 8 B 14.4365 24.8445 37.7364 H 227.782 That is, 0.00 0.05 0.48568 1.272 0.1 0.33288 1.458 0.2 0.23895 1.611 0.3 0.17980 1.779 0.4 0.13021 1.973 0.5 0.08646 2.261 0.6 0.05510 2.628 0.7 0.03079 3.190 0.8 0,01414 4.136 0.8660 Sin. 60°. 0,00532 5.729 In order to determine the radii of the 1. The last stars visible to the naked eye, according to Argelander, are at the distance of 8.8726 times unity, or nearly nine times the distance of the stars of the first magnitude. 2. The last stars of the ninth magnitude, which Bessel has descried in his zones, are at the distance of 37,73 unities, or nearly thirty-eight times the distance of stars of the first magnitude; and, 3. The extreme stars descried by Sir W. spheres containing the first six classes of Herschel in his sweeps with his 20-feet stars, or those between the first and the sixth telescope, are 227.8 unities, or two hundred magnitude, M. Struve takes as the basis of and twenty-eight times the distance of the his calculation the stars in our northern he-stars of the first magnitude, or 25.672 times more remote than the stars of the sixth misphere, as given by Argelander in his Uranometrie. Thus :magnitude, or the farthest seen by the 3 4 5 naked eye. Magnitudes, 12 No. of Stars, 9 34 96 214 550 2342 and from these numbers he obtained the 6 following results, the unity in the second eye : *The radius of the sphere containing all the 20 millions of stars above mentioned being unity. M. Struve next directs our attention to a ing "the extinction of the light of the fixed new and very singular speculation, respectstars in its passage through celestial space." So long ago as 1823, Dr. Olbers, in a memoir On a transparency of the celestial spaces, assumed that in the infinity of space there existed an infinity of created worlds, 1 -of suns, each of which, like our own, [feet is 61.18, 31.83-74.89 times the shone with its own light and on this suppo- distance of the stars 6. A, or 74.83-+8.876 sition, he demonstrated that the whole 663.96 times the mean distance of stars. visible heavens should shine with the lustre of the first magnitude. But instead of equal to that of our own sun. But as such 74.83, the gauges of Herschel give us a condition of the firmament does not exist, 25.672 for the radius of the stars 6 A. It he infers that there must be such an absorp-follows therefore that the range of Herschel's tion of this sidereal light as to reduce it to telescope, as determined by astronomical obwhat we now see in the heavens. In pro-servations, exceeds by scarcely one-third ducing such an effect, he proves that an the range which corresponds to its optical absorption of 1-800th part of the light of force. How are we to explain this fact, each star in its passage through a distance asks M. Struve? I can see no other explanaequal to that of Sirius from the sun, would tion, he adds, than that of admitting "that be sufficient. In favor of such a hypo- the intensity of light decreases in a greater thesis, no facts have been produced, but M. proportion than the inverse ratio of the Struve conceives that a proof of the actual squares of the distances, or what is the same extinction of light may be found in the enu- thing, that there exists a loss of light, an exmeration of stars of different orders of tinction, in the passage of light through brightness, and that even the rate of extinc- celestial space." In computing the amount tion may, within certain limits, be deter- of the extinction, M. Struve finds that it is mined. one per cent. for stars of the first magnitude (1 A), eight per cent. for stars of the sixth magnitude (6 A), thirty per cent. for those of the ninth magnitude (9 B), and eightyeight per cent. for the Herschelian stars, H. These views, which appear to us well founded, have been challenged by an eminent writer in the Edinburgh Review, who, while he admits the absolute infinity in the number of the stars, maintains that the foundation of the reasoning of Olbers and Struve may be "struck away," by certain "modes of systematic arrangement of the stars in space," which, "it is easy to ima The penetrating power of Sir W. Herschel's 20-feet telescope, he found to be 61.18, that is, by the help of this instrument, we can see stars 61.18 times more distant, than the last stars (sixth magnitude), which can be seen by the naked eye. This number 61.18, supposes the opening of the pupil, to be exactly 0.2 of an English inch, but as long-sighted and short-sighted persons have different powers of sight, the force of the eye is not a proper unity, in measuring the force of a telescope. M. Struve therefore substitutes for the eye a small achromatic telescope of 0.211 aper-gine," these modes being entirely in conture, and magnifying three times, which sonance with what we see around us of subwill introduce into the eye exactly the same ordinate grouping actually followed out." quantity of light that passes directly through It would have been desirable that the rethe pupil when its aperture is 0.2, while it viewer had stated one of these modes in gives a precise image, independent of the justification of this bold challenge. character of the eye. With this modulus, confess ourselves unable to conceive such a representing the eye as unity, he could mode of arrangement, although we cannot almost double the number of the stars con- agree either with Olbers or Struve in their tained in the maps of Argelander, or to conclusion, that the extinction of light, if it speak more exactly, he counted 183 when does exist, proves that sidereal space is only 100 were in the same space in the filled with some fluid such as ether, which is map. In taking, therefore, for unity the capable of intercepting a portion of the light distance of the last stars of the sixth mag- which it transmits. To fill infinite space nitude (6 A), which Argelander has seen, with matter, in order to explain a phenomethe visual radius or penetrating power of non, seems to us the very last resource of a the Herschelian modulus will be 31.83 sound philosophy. The sun has an atmo=1.2231, or equal to 1.2231+8.8726-sphere widely extended in the apprehension 10.582 times the mean distance of a star of of every astronomer The planets have atthe first magnitude, but Herschel has deter-mospheres too: our solar system boasts of mined photometrically that this radius is equal to twelve times the distance of stars of the first magnitude, a remarkable coincidence which could scarcely be expected. Hence the range of the telescope of twenty of about 700 recorded comets; and M. Arago is of opinion that if the perihelia of comets are distributed throughout the system *Edinburgh Review, January 1848. No. 175. Probable Error. Absolute +0.349 0.080 61 Cygni,* +0.103 0.053 +0.046 0.200 +0.133 0.106 +0.127 0.073 +0.082 0.043 as between the sun and the orbit of Mercury, minutes, and by means of four micrometer there would be three and a half millions of microscopes, its indications can be read off comets within the sphere of Uranus. Within to the tenth of a second. The telescope has the sphere of Neptune, of course, there an aperture of six inches diameter, and a must be many more; and Capt. Smith, in magnifying power of 215. The following mentioning the opinion of Arago, adds, are the results which he obtained :that there are many considerations which, on the same hypothesis, would greatly increase that number. If we consider, also, the enormous extent of the tails of these bodies, some of them millions of miles long, and the increase in the dimensions of comets as they recede from the sun, we shall have no difficulty in concluding that, within the limits of our own system, there is an immense mass of atmosphere or nebulosity capable of extinguishing a portion of the light which falls upon it. Let us, then, fill the infinite universe with similar systemswith similar obstructions to light, and we shall not require an ethereal medium to account for the want of luminosity in the starry firmament. The reviewer whom we have quoted, not satisfied with an instantaneous demolition of the speculation of Olbers and Struve, again slays the slain. "Light, it is true," he says, "is easily disposed of. Once absorbed, it is extinct for ever, and will trouble us no more. But with radiant heat the case is otherwise. This, though absorbed, remains still effective in heating the absorbing medium, which must either increase in temperature, the process continuing, ad infinitum, or, in its turn, becoming M. Struve :radiant, give out from every point, at every instant, as much heat as it receives." do not think that we are in a condition to draw this conclusion. The law of the transmission of heat through the celestial spaces is a problem unsolved; and till we can explain how the luminous and chemical rays of the Sun reflected from the Moon, are transmitted to the earth, while those of heat cannot be exhibited, even when concentrated by the most powerful burning instruments, we are not entitled to urge the objection of the reviewer. We M. Struve concludes his interesting report by giving us an abstract of the unpublished but highly interesting researches of M. C. A. F. Peters, of the Central Observatory of Pulkova, on the Parallaxes and Distances of the fixed Stars. After a historical notice of the labors of preceding astronomers on the subject, M. Peters determines the actual parallaxes of the stars from observations made with the great vertical circle of Ertel. This noble instrument, forty-three inches in diameter, is divided into every two a Distances No. of Julian expressed in years in which radii of the light traverses Apparent magnitudes. Parallaxes. Earth's orbit. these distances 1 A 0.209 986000 15.5 1.5 A§ 0.166 1246000 19.6 2.A 9.5 B * Bessel makes it 0". 348 0". 010. mediate magnitude, between those of the first and second and the second and third magnitudes. The magnitudes 1.5 and 2.5 are stars of inter |