In a communication to the ninth volume (new series) of the "Scientific American," Mr. H. P. Tuttle briefly names some of the most remarkable evidences of the progress of astronomy-a progress, he thinks, behind that of few, if any, of the other sciences-since the beginning of the current century. To the six planets only that were known at the end of the year 1800, we are now able to add 80 others which have been since discovered-79 of them directly by aid of the telescope, and one (Neptone) by its use guided by mathematical deductions from observed phenomena of other planetary bodies. In case of Saturn a new ring and a new satellite have been disclosed. Up to 1812, but one comet (Halley's) was certainly known to return: before the close of 1858, there had been added to the list of periodical comets 9 whose periods vary from 3 to 70 years, and about 20 with periods ranging from 100 to 10,000 years; while nearly 100 are now known whose orbits are of sensibly parabolic form. Again, while Sir Wm. Herschel was the first to detect the existence of multiple stars-usually binary, or as these are commonly called, "double"-more than 100 instances of such pairs or sets of stars, the members of each of which have a mutual revolution about their common centre of gravity, are now known. In case of some of these double, or generally speaking, "multiple suns," one complete revolution of the sort here referred to, and part of a second, have been already noted. In theoretical astronomy, Dr. Hansen's new tables of the moon, and Leverrier's new tables of the sun, Mercury, and Venus, now enable the astronomer to calculate with an accuracy far exreeding that before attainable the celestial phenomena which were taking place twenty centuries ago. Of course, a chief and indeed indispensable means to all these important results, has been the single device of the telescope. Asteroids-In the preceding volume was given a list of the minor planets from (51) to (76) inclusive-the period of their discovery extending from the year 1857 to Oct. 1862; and also certain particulars of interest connected with the discovery of some of these. Astronomers appear as yet to allow asteroid (75) to retain its place, subject to the result of future observations. The record for 1862 is, then, to be completed by the discovery, Nov. 12th of that year, of asteroid (77) by Dr. C. H. F. Peters, of Hamilton College Observatory. This planet, however, which was at the time near to Feronia, and corresponded in brightness with a star of the 11-12th magnitude, very soon eluded observation, and may even require discovery de novo. No name appears to have been assigned to it. Asteroid (78) was found by Dr. Luther, of Bilk, March. 15th, 1863. It appears as a star of the 10th magnitude, and was named by its discoverer Diana. On the Light of Sept. 14th, of the same year, Prof. J. C. Watson, of the observatory at Ann Arbor, Michigan, discovered asteroid (79). This planet which shows about the 10th magnitude, was independently discovered by M. Tempel, at Marseilles, Oct. 3d and 4th; and later elsewhere. Prof. Watson has chosen for it the name of Eurynome. The supposed asteroid (80) announced by M. Schmidt, of Athens, proves to be an instance of erroneous observation-the before known planet, Hygeia, having in fact been rediscovered. Thus, the record of these discoveries, from Oct. 1862 to Oct. 1863, is as follows: 1962, (77).. by Dr. Peters. 1863, (78) Diana,. Dr. Luther. "Prof. Watson. 66 (79) Eurynome, Comets.-Comet III, 1862, announced in the preceding volume as discovered by Dr. Bruhns, was first detected about three days earlier (Nov. 28th), by Professor Respighi, of Bologna. The discovery of Comet I, 1863, is mentioned in the account of last year. Comet II, 1863, was found, April 12th, by M. Klinkerfues, in right ascension 3092, declination 3° south. On the 19th of May, it was 10° distant from the north pole, and appeared as a round nebulosity, 5' to 6' in diameter. Comet III, 1863-by Respighi, April 13th, near B Pegasi. Its nucleus then had the brightness of a star of the 6th magnitude; April 25th, the tail had a length of 2°. Comet IV, 1863, was found, Oct. 9th, by M. Bäcker, of Nauen. Like the other comets of the year thus far named, it was telescopic merely. It attained its greatest brilliancy, Dec. 8th; perihelion Dec. 27th. Comet V, 1863-by M. Tempel, Marseilles, Nov. 4th; this was visible to the naked eye, its nucleus nearly stellar. Comet VI, 1863, was observed by M. Schmidt, at Athens, in the month of December. In a supplementary page inserted in the "Amer. Jour. of Science," January, 1864, appeared a note from Prof. Watson, of the observatory at Ann Arbor, in relation to the (supposed) discovery of a new comet by him, on the evening of January 9th, 1864. The comet was then quite large and bright, with a nucleus strongly condensed at the centre, and a tail 1° in length. From observations continued to the 12th, Prof. W. inferred a resemblance, in the elements of the orbit to that of the comet of 1810; and he remarks that subsequent observations must determine whether the comet had returned in the interval. In a later communication (“N. Y. Evening Post," Feb. 1st), he states that the comet would be very near the earth about the date just given, and suggests an attempt to determine by it the solar parallax. It does not yet appear that these anticipations have all been well grounded. In the "Evening Post" of February 6th, appeared a letter from Messrs. Silliman and Dana, inclosing a communication of Mr. D. M. Covey, of Southville, N. Y., dated December 26th, 1863, and addressed through the "Herald of Progress" to Prof. D. Trowbridge, in which Mr Covey gives an account of a comet first seen by him, November 21st, preceding, in declination, nearly 15° N., and right ascension 200°. On that date, it had the size of a star of the third magnitude; its course was afterward found to be northeastwardly, from Arcturus toward Vega in the Harp; its brilliancy was diminishing, and it soon became invisible to the naked eye. Messrs. Silliman and Dana say there is hardly a doubt that this was the comet described by Prof. Watson, and detected (it now seems), a few days previously (Dec. 28th, 1863,) by Respighi, of the University of Bologna. The most remarkable circumstance in the case is, that a comet visible to the naked eye should be present in the heavens a full month before its discovery was made at any observatory; but it was visible at about five o'clock A. M., an hour when most astronomers have concluded their labors. Spectra of Fixed Stars, Etc.--The results thus far arrived at in the way of determining the character of the spectra of different fixed stars, and others of the heavenly bodies, and hence, by inference, their physical and chemical constitution, are as yet to some extent at variance. This, indeed, was to be expected in the outset of observations of so extreme delicacy, conducted by different persons, with different forms of apparatus, and under differing conditions of the terrestrial atmosphere. Prof. Donati finds, in the case of nearly all the stars which have been examined both by M. Frauenhofer and himself, different systems of fixed lines from those originally laid down by the latter; and some differences, again, exist between the systems given by either of these and the spectra of the same stars as noted by M. Secchi in Italy, by Mr. Rutherfurd in New York, and by Dr. W. A. Miller and Mr. Wm. Huggins in England. Frauenhofer had not condensed upon his prism the light of the star to be examined, but placing the prism and a cylindrical lens before the objective of a small (observing) telescope, he directly viewed the spectrum afforded by analysis of the light, of such intensity as it naturally fell upon the apparatus. The cylindrical lens was to supply the place of the fine slit between knife-edges first employed for the solar spectrum by Wollaston; such a lens acting to elongate the image of the star in one direction only, or to a line, and giving to the spectrum the desired breadth without increasing its length. Mr. Rutherford (" American Journal of Science," Jan. and May, 1863) states that throughout the course of his observations he received the light through a slit on its way to the prism; but that, finding that the necessity of throwing the star slightly out of focus occasioned a considerable loss of light upon the jaws of the slit, he was later led to add to the arrangement the use of the cylindrical lens-introduced between the objective of the condensing telescope and the prism--and with the effect of largely increasing the light, and, of course, the distinctness of view of the parts of the spectrum obtained. The lens is useful only in the analysis of merely luminous points, as the stars may be assumed to be, and not in case of the planets, sun or moon. Excepting the addition now named, the spectroscope was simply that of Bunsen and Kirchhoff, "consisting of a condensing telescope with adjustable slit, a scale telescope with photographed scale of equal parts showing bright lines upon a dark ground, a flint-glass prism of 60°, and an observing telescope with Huyghenian eye-piece, magnifying about five times." If the telescopes be not perfectly achromatic, some change of focus will be required in order favorably to observe the different regions or colored spaces-the ultra-red rays requiring a slight, and the violet and indigo a considerable, change of focus from that answering for the intervening portion of the spectrum. For exact comparison of different observations, the place of the sodiumline D was, in each instance, brought to coincide with the division of the scale marked 20. With the apparatus so adjusted, the locations of the seven principal lines of the spectrum of sunlight, as determined by Mr. Rutherfurd, are as follows (the letters reading of course, from red to violet): B 33.1, C 32.3, D 30, E 27, 26.5, F 24.4, G 19.3, II 14.5. 13.9. By means of a plate (highly valuable for reference) he gives a comparative view of the spectra of the sun, moon, Jupiter, Mars, and 17 of the brighter among the fixed stars. In the lunar spectrum he finds the principal solar lines, B, C, D, E, and F, and he supposes that G may yet be detected. The lunar lines just named are very strong and well defined; and other marked features are beyond F, a broad faint band at 21.05,a broad line at 19.9, and a broad dark line at 18.09. Most noticeable in the spectrum of Jupiter are the distinct line D, and two broad bands respectively at 32.1 and 31.12; in that of Mars D is wanting, though there is a well-defined line near its place, at 30.25, other strong lines at 27.1 and 26.55, and a broad band at 24.4. Without attempting to fix upon any final principle of classification for the stars he has examined, Mr. Rutherfurd for the present divides their spectra into three groups: "first, those having many lines and bands, and most nearly resembling the sun-viz., Čapella, B Geminorum, a Orionis, Aldebaran, y Leonis, Arcturus, and 3 Pegasi. These are all reddish or golden stars. The second group, of which Sirius is the type, present spectra wholly unlike that of the sun, and are white stars. The third group, comprising a Virginis, Rigel, etc., are also white stars, but show no lines; perhaps they contain no mineral [query-metallic? substance, or are incandescent without flame." Taking Capella and Sirius as good examples of the first two classes of stars just named, their spectra are thus described: Capella-a line respectively at 30.22, 27.73, 27.38, 26.75 and 24.78; Sirius-a broad black line, or band, respectively at 32.4, 24.8, 19.9, 16.8; the limit at 14.5. In the spectrum of this last star no fine lines have been found; the lines observed are all broad and black, with margins well defined, being in fact so many complete interruptions of the colored field. The spectrum of a Orionis is marked by three broad bands, that of Aldebaran by four, and that of ẞ Pegasi by eight, these in all cases lying mainly within the less refrangible half-length of the entire field; and all these, as well as the bands in the light of Jupiter, are supposed by Mr. Rutherfurd to be absorption bands due to the atmosphere of the respective bodies, but which may yet possibly be resolved into lines. In conclusion he alludes to the evidence now possessed to the effect that the stars differ in their constituent materials, and asks "What then becomes of that homogeneity of original diffuse matter which is almost a logical necessity of the nebular hypothesis?" In his second article he mentions having added a prism by means of which the spectrum from a spirit lamp is constantly present in the field of view. He finds this a most useful check, and by means of the comparison so afforded he has proved the presence in the spectrum of Arcturus of the lines D, E, b, and G, and has become almost certain that each line furnished by its light has its counterpart in the solar spectrum. M. Secchi, of Rome, has used a Janssen's spectrometer of direct vision, and he is astonished at the magnificence of the results-probably favored by an unusually pure atmosphere -which he thus obtains. He has published the determinations only of five stars. He finds in a Orionis a line at F, and four between Fand G, where one only is given in the Greenwich observations. The spectrum of Aldebaran is of greater extent, and 16 bands of various breadths were noticed in it. He finds a spectrum of Rigel, as well as of Sirius, both white stars; these are longer than the spectra of red stars, and in the former also the prominent lines appear chiefly in the blue and violet spaces at one extreme, and the red at the other. The band F, which so far would appear to be as prominent in the light of all the stars as it is in that of the sun, Secchi thinks, may be due to absorption by our atmosphere. Mr. Huggins and Dr. Miller have examined a The Sun and Stars Photometrically compared. gives "Amer. Journal of Science," July, 1863) Suppose a lens of known focal distance, say In the use for this purpose of a convex lens, the measure is commenced at the focal point: and the number of times the diameter is reduced is equal to the number of focal distances the lens is removed less one (e. g., 11 focal distances, less 1, give a reduction of ten times in diameter, and in brightness); but with a concave lens, the measure is the actual distance from the lens itself. For these observations Mr. Clark has an underground, dark chamber, 230 feet long, accessible at one end from his workshop, and communicating with the surface at the other end by a vertical opening, one foot A common plane silvered-glass mirsquare. ror, set at a suitable inclination over the orifice, reflects the rays of the sun or star down the vertical opening in the ground upon a prism so placed as to throw the light, by total reflection, in the line of the axis of the horizontal chamber; and no light can enter the latter save through this lens. To the side of the prism facing the chamber is cemented with Canada balsam (so perfectly as to render the two optically one medium) the flat side of a planoconvex lens, say of 1-20th of an inch focus. Then an observer in the cellar 230 feet distant sees through this lens the sun reduced 55,200 times; and its light varies little from that of Sirius. To multiply the reducing effect, a second lens of known focal distance, say 6 inches, is mounted on a little car, which, by cords and a pulley, can be sent to any required distance on a track toward, and in the line of, the fixed lens. At noon, March 19th, with a perfectly clear sky, Mr. Clark found the sun barely visible through the two lenses when the movable one was 12 feet from the eye, and when being 218 feet from the fixed lens, the reduction given by the latter alone was 52,320 diameters, and the multiplying effect of the second lens = 12 x 2 - 123 times, the total reduction being thus 1,203,360 times. By observations expressly devised for such purpose, he concludes that the proportion of the light of the sun or a star that will be lost in these experiments by the extinguishing action of the mirror, prism, and lenses, will be in effect almost exactly compensated by the additional light also reflected by the mirror from a small region of sky just about the sun or star. Proceeding upon this admission, the following are the results at which, in his earlier observations, Mr. Clark arrived; The sun is visible when reduced....1,200,000 times. The full moon.. Sirius... Procyon.. Pollux.. Castor.... 3,000 The following comparisons will show the relation in which these results stand to the measures of the sun's light previously given by Dr. Wollaston, and by Mr. Bond, of Harvard College Observatory. To reduce our sun to the brightness of the star a Lyra, the distance of the former must be increased, according to Wollaston, nearly.. Bond, Clark. 425,000 times. 155,000 ..102,000 66 66 of entire extinction of the light which would otherwise reach us from the larger proportion of the stars of those regions. But Mr. Clark suggests, what is obviously true, that if differ ent stars actually differ in original or inherent splendor, then it will be the least luminos which at any given distance will first elude the eye, and as the distance is increased, a continually larger proportion of all the stars will thus -as a simple effect of reduction by increasing distance-disappear; so that the sparseness of stars in the outermost yet penetrated regions of the universe does not necessarily prove the presence of an absorbing medium, or ether, be tween their place and the earth, but may mere ly illustrate the known and simple relation of the apparent magnitude or brilliancy of a visi ble object to its distance. The Question of the Sun's Distance from the Earth.-Professor Joseph Lovering, of Har vard College, has communicated to the "Amer ican Journal of Science" (Sept., 1863), a highly important paper upon the subject of the sun's distance from the earth, as computed from the several sorts of data relied on, and especially upon the remarkable variance of the result very recently obtained by M. Foucault from previous calculations, and the general effect of this va riance, if confirmed, upon the distances and magnitudes of the various astronomical bodies First, as to the usual methods for determin And the light received from these luminaries ing the sun's distance: To see the distance of differs, according to Wollaston, as.. Bond, Clark, Mr. Clark's method, it will be seen, does not depend upon comparisons with artificial lights, but makes a simple reduction of the luminary observed to a minimum visibile, under the most favorable conditions of observation, the standard in all cases. In his later experiments, he prepared a close covering for the opening to the dark chamber, with a circular perforation, subtending at the prism an angle of 32", and substituted a lens of one-eighth-inch focal distance. Then, by use of two additional lenses, adjustable by sliding, and placed in a telescope tube properly darkened within, he found that it required on some occasions a reducing power of nearly 1,600,000 to send the sun completely out of sight. Mr. Clark shows that these observations have an important bearing on the question of the existence of an extinguishing medium in space. The more powerful telescopes reveal, in proportion to their power, a far less number of stars than are visible to the unassisted eye; in other words, the appearance is, as if the remoter fields of space were more and more thinly tenanted with stars, in comparison with the number within the sphere of direct vision. "This fact has been made an argument for an extinguishing medium in space; the greater sparseness of the more distant or telescopic stars being supposed due to the circumstance any body is an act of binocular vision. In cast of near bodies, the interval between the two eye is the base-line of a triangle of which straigh lines from the object to the eyes respective form the other two sides; and the sensation of effort in converging the eyes upon the object, guided by experience, gives us approximately the distance. As the object is farther removed the base-line must be taken greater, until, in attempts to determine the distance of the sun it is made the distance between two telescopes directed toward that body from points at the opposite extremities of the earth's diameter and certain parts of the triangle, giving th distance of the object, are now found by calen lation. The angle between the directions of the two telescopes is the "solar parallax;" and the distance of the sun will vary-the base-ing being supposed known-as the magnitude of this angle. Since a small error in the sola parallax would involve a large error in the sun's distance, astronomers select a planet com ing nearer the earth than the sun-either Ve nus, at inferior conjunction, or Mars at opposi tion. The former observation can only b made in case of a transit across the sun's dise the quantity determined being the differenc of parallax between Venus and the sun: viz. from about 21" to 25". From the combine observations of the two transits of Venus las occurring-1761 and 1769-Encke deduced the solar parallax as 8.57116. This correspond to a solar distance of 95,360,000 miles. Trans its of Venus will occur in 1874 and 1882; bu Encke declares they will be so unfavorable for observation that the reduction of error in the solar parellax by this means to within a limit of th of a second, is hopeless for at least The solar parallax, as two centuries to come. derived from that of Mars, in 1740, by Lacaille, was 10.20, with a possible error of 0".25; and in 1832, by Henderson, 9".028. Dr. B. A. Gould computed it from the first opposition of Mars observed by Lieut. J. M. Gilliss, 1849-152, in Chili, at 8".50. Various determinations of the solar parallax, from the law of gravitation, and based chiefly on perturbations of the moon's longitude, have placed it at from 7'.80 to 8".84; while the most recent by methods of the sort here referred to, are, that of Hansen in his new "Tables of the Moon," S".8762, and of Leverrier, 8".95. [Evidently, with a fixed base line, the greater the actual parallax, the less is the true distance of the sun from the earth. In a recent account of this same question, Mr. Hind calls attention to the fact that the deductions from the first transit of Venus, taken alone, gave a solar parallax of 8".9142, which is nearly as great as that of the most recent calculations based on other methods. He speaks of the increase of the solar parallax from the value found by Encke, and usually adopted, to about 8".95, as being now demanded by the concurrent results of six distinct authorities, among whom are some of those just named; but he thinks that in their calculations astronomers will retain the old value till the next transits of Venus; and, doubtless with a view to observations of these, he remarks that the important question which has recently been raised as to the existence of a large error in the estimated distance of the sun, may perhaps be set at rest in twenty years, though hardly in less time.] Römer, as is well known, by observations of eclipses of Jupiter's satellites, first determined the fact that the transmission of light through space requires time, and calculated from the time apparently occupied by the sun's light in crossing the orbit of the earth the velocity with which it must move. Delambre, from a discussion of 1,000 of those eclipses, deduced the time of the passage of light over the mean distance from the sun to the earth as 493.2 seconds; and 96,360,000 miles divided by this number gives 193,350 miles per second as the velocity of light. Again, taking the sun's distance as now given, the velocity of the earth in its orbit is 18.977 miles per second; and the velocity of light calculated by Bradley's principle of aberration-the amount of the aberration according to Struve being 20.45-is 10,088 times that of the earth in its orbit 191,513 miles a second. From Fizeau's experiment in 1849, with a revolving toothed wheel, the radiating teeth and included spaces of which alternately interrupt or transmit, according to the moments in which it is returned to the edge of the wheel, a ray of light reflected between distant mirrors, the velocity of light was calculated at 194,667 miles a second. Finally, Foucault has carried out, and apparently with entire success, the application suggested by Arago of Wheatstone's revolving mirror (with the addition of needful apparatus) to the purpose of determining the absolute velocity of light; and the result at which he arrives is a velocity equal only to 185,177 miles in a second. Now, this velocity is more than three per cent. less than the lowest usually accepted But Foucault (192,000 miles), as deduced from the sun's accepted parallax and distance. states that the extreme difference of results in the various trials made by him did not exceed th of the entire value; and he believes that the mean result can be trusted to the 5th part of the value; while the aberration adopted (20".45) in Bradley's method cannot be supposed at fault beyond the 6th part of the whole. How is the new velocity of light to be reconciled with the old value of aberration? This latter establishes the ratio of the velocity of light to that of the earth. And if this ratio must still be accepted, while one term of it (the velocity of light) must be diminished by three per cent., then inevitably the other term of the ratio must also be diminished, and proportionally. Is it possible that there is an uncertainty, to the amount of three per cent., in the orbital motion of the earth? Shall we have to reverse hereafter the usual mode, and determine the velocity of the earth in its orbit from that of light, accepting the latter as the better known of the two? The error in the earth's movement, if it be such, is an error not in time but in space. We cannot, as the slower terrestrial velocity would (on that side of the question) require, lengthen the year by about 11 days; hence we must, as the only other way of satisfying the new facts, diminish our estimate of the circumference of the earth's orbit; and of course, therefore, in like proportion les sen the mean radius of the orbit, i. e., the sun's mean distance. [It will be noticed that the recent tendency to a larger solar parallax has the same general effect as Foucault's reduction of the velocity of light; namely, to place the earth nearer to the sun.] Foucault's experiment on the velocity of light has been popularly announced as making a "revolution in astronomical science." Prof. Lovering judges that it has only attracted popular attention to an old difficulty, and perhaps given a solution of it. "Neither the velocity of light, aberration, nor the sun's distance can be [was?] suspected of an error to the extent of 3 or 4 per cent.; and yet one at least must be wrong to this degree, as the best values of the three elements are irreconcilable with each other. Which shall be changed? "It may excite surprise in those who have heard of the accuracy of astronomy, without weighing the exact significance of the word as applied to so large a subject, that there should still be a lingering uncertainty, to the extent of three or four millions of miles, in the sun's |