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the reduction of his work on the orbit of
of previous years, consisting of observations of double stars and satellites; observations for stellar parallax, with a series of drawings of Saturn by Prof. Asaph Hall; observations completing a catalogue of miscellaneous stars which has been in process of formation ever since the transit circle was mounted in 1866; observations of comets, asteroids, and occultations with the 9-inch equatorial; and the maintenance of the extensive time-service, the magnetic observations, and the testing of instruments for the naval service. Progress on the new buildings on the heights beyond Georgetown has been somewhat delayed, but the foundation walls of the main building and the greater part of the building for the 26-inch refractor were completed by the close of the year. The long disused observatory of Georgetown College, founded in 1846, and famous for the early labors of Secchi and Sestini, has been thor§ repaired under the supervision of the new director, Father J. G. Hagen, S.J., and important additions have been made to the equipment. For the present, observations are confined mainly to southern variables. At the Yale Observatory Dr. William L. Elkin has completed the heliometer measures for the triangulation of the region near the north pole, and a few observations of Iris, Victoria, and Sappho were obtained for the determination of the solar parallax in co-operation with the observatories at the Cape of Good Hope and at Leipsic. The heliometers at Bamberg and Göttingen will probably co-operate in the observations of Victoria and Sappho, and meridian observations at other observatories may also be obtained. Mr. Asaph Hall, Jr., has completed itan, his result being in very satisfactory agreement with the results of Bessel and Hermann Struve. The Cincinnati Observatory has a new meridian circle of 5% inches aperture, the objective being by Clark, and the mounting by Fauth & Co. The instrument does not differ materially from the Repsold type, and as far as Prof. J. G. Porter's investigations have gone, it compares well with the latter as an instrument of precision. The object-glass and micrometer ends are interchangeable; the cell of the object-glass is of steel, the lens being supported at three points. The telescope carries two circles of 24 inches diameter, one divided coarsely to half degrees, the other having two sets of graduations upon a silver band, both of them to five minutes of arc. The errors of graduation are found to be extremely small. At the Lick Observatory, Mr. J. M. Schaeberle has been observing fundamental stars with the meridian circle, Mr. Charles B. Hill has charge of the time service, and Mr. J. E. Keeler is engaged with the spectroscope. Mr. E. E. Barnard has been diligently at work upon the sun and nebulae with the 12-inch equatorial, and has made experiments in astronomical photography with the 36-inch. His discoveries of comets are reported elsewhere. Mr. S. W. Burnham has discovered and measured a number of faint double StarS. A still larger refractor than the Lick telescope has been projected—one of 40 inches aper
ture, for the University of Southern California at Los Angeles, and a bill was introduced in Congress at the last session making provision for a refractor of five feet aperture, which was to be mounted at the United States Naval Observatory. . It is, understood that the glass for the 40-inch lens has been ordered by Clark, the sum of $200,000 being available for the contemplated observatory, sufficient, probably, to meet the cost of the instrument. The scheme for the five-foot lens never received any support from the Government astronomers. The disks for the 20-inch equatorial of the Chamberlin Observatory, Denver, have been cast by Mantois at Paris, and will be worked by Clark. The mounting is well under way at the shop of Fauth & Co., of Washington. An illustrated description of the new Dearborn Observatory, at Evanston, Ill., will be found in the “Sidereal Messenger” for October, 1889. The fiftieth anniversary of the dedication of: the Hopkins Observatory of Williams College was celebrated in 1888, a discourse upon “The Development of Astronomy in the United States” being delivered by Prof. Truman H. Safford. The Hopkins Observatory seems entitled to the honor of being the first permanent American observatory, having been projected about 1834, chiefly built in 1837, and dedicated on June 12, 1838. The University of North Carolina had built an observatory in 1831, and had provided an excellent instrumental equipment, but in 1838 the building was partially destroyed by fire, and little or no work was ever done with the instruments. Prof. Samuel P. Langley has devised an apparatus for eliminating personal equation, especially in the observation of sudden phenomena, such as the disappearance of a star when occulted by the moon. The principle of the method consists in associating a motion, real or o of the object with intervals of time, so that the top. position of the object at the instant of the occurrence of any phenomenon being noted, the time of the occurrence will be known. Experiments made with artificial stars, which were given an apparent rotary motion about the axis of the observing telescope by a suitably arranged revolving prism, show that it was quite possible for a comparatively inexperienced person to observe an occultation with a probable error of only one fortieth of a second. A valuable series of papers on personal equation has been contributed |. Dr. E. C. Sanford to the “American Journal of Psychology,” vol. ii. Dr. W. Wislicenus, of Strasburg Observatory, has published an interesting account of a series of investigations made to determine the absolute personal equation in transit observations, not only for the horizontal position of the telescope, but for all inclinations. In the form of meridian circles made by Repsold, a little mirror can be cemented to the inner surface of the object-glass so as to reflect toward the eye end a portion of the light from the cube of the instrument. By placing a small convex lens behind the ocular, an artificial star is obtained which is easily moved in the plane of the reticule with a velocity corresponding to any declination. Dr. Wislicenus concludes from his experiments with this apparatus that the inclination of the telescope has a considerable effect upon the observer's personal equation, Foreign Observatories.—The Astronomer Royal reports that the routine work of the Greenwich Observatory—the determination of the positions of the sun, moon, planets, and a selected list of fixed stars, and magnetical, meteorological, and solar observations—has been continued as in previous years. A new dome has been built for a 13-inch photographic equatorial, Greenwich being one of the observatories to take part in the international photographic chart of the heavens, and progress has been made by Sir Howard Grubb in working the disks of the 28inch refractor which is to be on the StokesPickering plan, adapted to photography as well as to eye observations—a useful result, accomplished by making the crown lens reversible in its cell to get rid of the spherical aberration which is oilo by the separation of the lenses necessary for photographic correction. The observations for a redetermination of the difference of longitude between Paris and Greenwich were completed in the autumn of 1888. Prof. Piazzi Smyth has resigned the appointments (which he has held since 1846) of Regius Professor of Practical Astronomy in the University of Edinburgh and Astronomer Royal for Scotland, and he has been succeeded by Dr. Ralph Copeland, of Dunecht. The Dunsink Observatory has a new reflecting telescope of 15 inches aperture: the gift of Isaac Roberts, which is to be applied to photographic researches upon stellar parallax, a field of investigation which has articularly engaged the attention of Prof. C. ritchard at Oxford. Prof. Pritchard reports that preparations for taking part in the international scheme for photographing the heavens are well advanced. Cambridge University, England, has received a most valuable acquisition to its instrumental §". in a 25-inch refractor, the gift of r. Newall. At Paris the most important addition to the instruments is the apparatus devised by M. Loewy for the investigation of the constants of aberration and refraction: a new determination of the latitude is in progress, and the Henry brothers o their experiments in celestial photography. R ow observatory, with a 104-inch Repsold refractor and 4-8-inch Repsold meridian circle, has been established at Vienna by Herr von Kuffner, and an admirably equipped observatory, founded by Dr. Carl Rameis, has been built at Bamberg. It is reported that the Pope has decided to establish a new observatory at the Vatican, which will probably cost $200,000. An observatory has been founded at Tokio, Japan, under the direction of H. Terao, by combining the astronomical departments of the old marine observatory, the observatory of the Ministry of the Interior, and that of the imperial university. The principal instruments are a 54inch transit, 5-inch meridian circle, and equatorials of 7-inches and 8-inches aperture. Astronomical Photography.—Prof. Pickering has published a research upon the brightness of stars as determined photographically, taking up the examination of three regions of the sky for the formation of preliminary standards.
These are the Pleiades, the region around the #. and a number of stars along the equator. His results are satisfactory, and it seems likely that if the errors in the photograph plates themselves can be eliminated, the subsequent estimation of a star's magnitude can in this way be made at least as accurately as by the ordinary photometric methods. Dr. Elkin has compared Gould's reductions of Lewis M. Rutherfurd's photographs of the Pleiades, taken over twenty years ago, with measures made by the heliometers at Königsberg and New Haven. The smallness of the probable errors Dr. Elkin regards as a convincing proof that in photography we have a means of investigation for micrometric work at least equal to any existing method as regards exactitude, and doubtless far surpassing them in ease of measurement and output of work. In this conclusion he is strengthened by experiments made with the 36inch equatorial at the Lick Observatory, in conjunction with Messrs. Burnham and Barnard. International Astro- photographic Congress.-The work of the Permanent Committee of the International Photographic Congress, organized at Paris in 1887, has been prosecuted with vigor. The general plan of the undertaking, the object of which is to provide a photographic map of the whole sky which shall include stars as faint as the fourteenth magnitude, has been described in the “Annual Cyclopaedia” for 1887. Since that time four numbers of a “Bulletin " have been published, under the auspices of the Institut de France, containing reports of preliminary experiments and correspondence relating to the details of the work. At the meeting of the Permanent Committee in o: tember, 1889, it was decided to adopt a field 2° square for the photographic plates. The question of the reproduction of the plates and of the publication of the map was left open, but it is robable that one or more bureaus will be estabished for measuring the hegatives obtained at observatories not provided with special apparatus for the purpose, and photographic copies of all plates will be preserved in selected places in case of accident to the original negatives. A series of standard plates will be prepared by the Paris Observatory, and the time of exposure must be adjusted so as to compare properly with these standards. Thus far no observatory in the United States is upon the list in the assignment of zones. A bill was introduced in Congress for the purpose of enabling the United States Naval Observatory to undertake a share of the work, but none of the private observatories have signified their intention of co-operating. This is partly due without doubt to the considerable expense involved, but it is also due to the fact that there is in the minds of some astronomers most competent to . judge, a doubt as to whether the best form of telescope has been selected by the Congress: moreover, the main difficulty seems to lie not in obtaining the photographs, but in reproducing and measuring them, and in converting the measures into right ascension and declination, so that they may be of practical value. Among the papers of interest in the fourth part of the “Bulletin” referred to, is one by Dr. H. C. Vogel, describing the photographic refract
or recently constructed for the observatory at Potsdam by the Repsolds. This instrument has two objectives; eye-piece and plate-holder are in the same tube, conforming to the resolutions of the Congress in 1887, but the peculiarity is in the form of mounting, which is quite different from both the English and the French forms. The illar that supports the polar axis is not o: i. L-shaped, the lower part being inclined nearly in the plane of the equator, the upper almost at right angles to this, extending toward the north pole and inclosing the polar axis. The support possesses very great stability, and its form permits an uninterrupted motion of the telescope in all positions. The seven instruments the construction of which was given to Messrs. Henry and Gautier are finished. The three destined for the observatories of Bordeaux, Toulouse, and Algiers have been delivered, and the four for La Plata, Santiago, Rio de Janeiro, and San Fernando are also finished and in course of shipment. These seven observatories, with that of Paris, will be ready to commence work in the first half of the coming year. Another paper of great interest is contributed to the same number of the “Bulletin” by Herr Reuz, of the Pulkowa Observatory, who has used a negative by the Henrys for determining the places of the stars occulted by the moon on Jan. 28, 1888; he finds that they compare satisfactorily with such meridian observations as are available. The committee—Messrs. J. Janssen and A. A. Common—to whom was referred the question of organizing and co-ordinating the work of those interested in various branches of astronomical o other than the chart of the sky, issued in June, 1889, a circular to astronomers calling a meeting at Paris on the 22d of August. This meeting was subsequently postponed to Sept. 20. The circular referred to the desirability of obtaining a complete photographic record of solar phenomena; , photographs of the solar spectrum; a systematic description of the lunar surface by photography on a large scale; photographs of planets and their satellites, both descriptive and for the purpose of measurements; photographs of meteors, comets, and particularly of nebulae, clusters, and of stellar spectra. Motion of the Solar System in Space.— An important contribution to our knowledge of the motion of the sun with its attendant planets through space is given by Dr. Ludwig Struve in a paper published in the memoirs of the St. Petersburg Academy. Dr. Struve takes as the basis of his investigation the proper motions of over 2,500 stars derived from a comparison of the Pulkowa catalogues of 1855 with Auwers's rereduction of Bradley, 1755. He finds that the solar system is moving toward a point in the constellation Hercules, the co-ordinates of which are right ascension 273.3°, declination + 27.3°, the amount of the motion in one hundred years being 4-36", as seen from an average sixth-magnitude star. The actual velocity corresponding to this is about thirteen miles a second. By combining his result with those of other investigators, Dr. Struve adopts as the most trustworthy co-ordinates of the sun’s “goal,” to use a term introduced by Prof. Herbert A. Newton in connection with the motions of meteors,
A = 266.7° and D = + 31.0°. This point is still in the constellation Hercules, and the mean velocity is found to be fifteen miles a second. Eclipses of 1889.-During 1889 the ephemeris shows three eclipses of the sun–Jan. 1, June 27, and Dec. 21—the first and last total, the second annular; and two eclipses of the moon–Jan. 16 and July 12. The solar eclipse of January, the last total solar eclipse visible in the United States in this century, was very successfully observed in California and Nevada, and a somewhat detailed account of the observations is given below. The eclipse of the moon on Jan. 16 was observed at Lick Observatory, but nothing of interest was noted. Dr. Arthur Auwers and Dr. David Gill, at the Cape of Good Hope, obtained measures of cusps with the heliometer during the annular eclipse of June 27. Of the partial eclipse of the moon on July 12 nothing of interest is reported. For observing the total solar eclipse on Dec. 21, three stations are available—the southwest corner of the island of Trinidad, where totality will last for 1" 46°, the sun's altitude being 12°; Cayenne on the coast of French Guiana, totality 2m 3", altitude 24°; and a point on the western coast of Africa about 100 miles south of St. Paul de Loanda, totality there lasting 3" 12", with the sun at an altitude of 46°. It is all the more desirable to make the most of this eclipse, as another total eclipse of the sun will not occur till April, 1893. A party has therefore been sent out by the United States Government to the western coast of Africa, and a party from Lick Observatory will occupy a station at Cayenne. Other stations will be occupied by parties from England and the Continent. he Total Solar Eclipse of Jan. 1, 1889. —The event of chief astronomical interest in 1889 was the total eclipse of the sun, which occurred on New Year's day. The moon's shadow first touched the earth at a point not far from the Aleutian Islands, and passed southeast and then northeast, striking the mainland at Point Arena, Cal., where totality began at 1.30 P.M., and lasted two minutes. The line of central eclipse then crossed California, Nevada, Idaho, Wyoming, Montana, and Dakota, and finally left the earth at a point about in the center of Manitoba, the duration of totality diminishing as the shadow moved east from Point Arena. In California the average width of the belt of totality was about 96 miles, in Nevada 90, Idaho 82, and Montana 66 miles. The partial phases of the eclipse were visible over the greater part of North America, the first contact being observed at Washington, a few minutes before sunset. Ample preparations were made for utilizing to the utmost the less than two minutes of totality. Carefully prepared suggestions and instructions were issued by Lick Observatory and by Prof. David P. Todd, of Amherst, for enlisting the interest of as many amateur astronomers and photographers as possible, and, as the weather was generally favorable, the result was a great number of sketches, photographs, and miscellaneous observations. The most thoroughly equipped party in the field was that from Harvard Observatory, under charge of William H. Pickering, at Willows. Cal. This party alone secured between 50 and 60 photogo. taken with 14 telescopes or cameras and spectroscopes, one of the telescopes being of 13-inches aperture, the largest ever used in observing a total eclipse of the sun. Through
ECLIPSE of the sun, JANUARY 1, 1889.
the kindness of Prof. Pickering, we are able to reproduce a photograph taken with this instrument, which shows wonderfully well the filamentous structure of the corona. A party from Lick Observatory, under Mr. Keeler, was at Bartlett Springs; one from Washington University o: St. Louis, under Prof. Henry S. Pritchett, at Norman; one from Carleton College, at Chico; and many other available points were occupied by individual astronomers or photographers. At Cloverdale, the Pacific Coast Amateur Photographic Association was represented by thirty cameras. A report from Lick Observatory, containing the observations of the Lick party at Bartlett
Springs, and also reports from many co-opera
tors all over the State, including those from the Amateur Photographic Association, has been ublished with characteristic promptness by rof. Edward S. Holden. The Smithsonian Institution has published a series of photographs of the corona on a uniform scale, copied from a collection of positives on glass kindly presented by various observers, and has also published a suggestive paper by Prof. on. Bigelow, wherein he traces a close agreement between magnetic lines of force computed for the sun, and the curves of the polar filaments shown upon the Pickering photograph. The detailed report of the Harvard party has not yet a peared. Prof. H. A. Howe, of o Observatory, at Denver, describes his own observations and those of his co-operators at Winnemucca, Nev., as the initial publication of his new observatory, and many preliminary reports are contained in current journals. The frontispiece of Lick Observatory report is an admirable photograph of the corona, by Barnard, which seems to compare favorably with Pickering's, though one was taken with an object-glass of 13-inches aperture specially made for the purose, and |. other with a little telescope of 34inches aperture stopped down to 1% inch and
uncorrected for photography. The volume contains also a careful o, by Prof. Holden of Barnard's photographs and of all the photographs and sketches transmitted to Lick Observatory. We quote briefly Prof. Holden's conclusions, which may be regarded as representing the results from this eclipse as far as they are at present attainable:
I. That the characteristic coronal forms seem to vary periodically as the sun spots (and auroras) vary in frequency, and that the coronas of 1867, 1878, and 1889 are of the same strongly marked type, which corresponds, therefore, to an epoch of minimum solar activity. II. That so-called “polar” rays exist at all latitudes on the sun's surface, and are better seen at the poles of the sun, simply because they are there projected against the dark background of the sky, and not against the equatorial extensions of the outer corona. There appears to be also a second kind of rays or beams that are connected with the wing-like extensions. These latter are parts of the “groups of synclinal structure” of Mr. Ranyard. III. The outer corona of 1889 terminated in branching forms. These branching forms of the outer corona suggest the presence of streams of meteorites near the sun, which, by their reflected light and by their native brilliancy, due to the collisions of their individual members, may account for the phenomena of the outer corona. IV. The disposition of the extensions of the outer corona along and very near the plane of the ecliptic might seem to show that, if the streanus of meteorites above referred to really exist, they have long been integral parts of the solar system. ote.—The conclusions III and IV appear to be contradictory to that expressed in I. The electrical theory announced by Dr. Huggins in the Bakerian lecture for 1885 seems to reconcile the conclusions I, III, and IV. W." The P. of the corona which were taken just before contact II and just after contact III rove the corona to be a solar appendage, and are atal to the theory that any large part of the coronal forms are produced by diffraction. . . . VI. The spectroscopic observations of Mr. Keeler show conclusively that the length of a coronal line is not always an indication of the depth of the gaseous coronal atmosphere of the sun at that point, and hence to indicate the important conclusion that the true atmosphere of the sun may be comparatively shallow. VII. Mr. Keeler draws the further conclusion in his report . . . that the “polar” rays are due to beams of light from brighter areas of the sun illuminating the suspended particles of the sun's gaseous envelopes. In order that this conclusion may stand, it is necessary to show that all these “polar” beams are comsed of rectilinear rays. . . . . An important concluion from [the photographic and photometric] measures seems to be that it is impracticable to photograph the corona in full sunshine with our present plates, and that a photographic search for Vulcan is hopeless. The Sun.—H. Crew, whose observations of the rotation of the sun were noted in last year's summary, has recently made a new series of observations for the correction or confirmation of the conclusion that the angular velocity of rotation increases with an increase of latitude. He still finds shorter rotation periods for the higher latitudes, the mean value for the period at latitude 45° being eighteen hours shorter than at the equator, but, owing to the smallness of this difference and to the uncertainty of the observations, he is of the opinion that “no certain variation of period with latitude has been detected with the spectroscope.” Attention is called. however, to the wide differences of the equatorial period as obtained by different methods—differences that may be due to the fact that we are really dealing with different strata of the sun, though here, also, too much reliance must not be placed upon the observations. During 1888 sun-spots were few, small, and in low latitudes, and there were frequent intervals in which no spots at all were seen—longer intervals, in fact, than any since the minimum of 1879. The most prolific month as to entire spotted area, though not as to number of spots, was November, following immediately a long period of quiescence. There was a rough tendency of spots to certain solar longitudes; and in latitude they continued to be more numerous in the southern than in the northern hemisphere. Faculae did not vary simultaneously with spots, but their diminution as compared with 1886 and 1887 was slight. o showed a very noticeable development during the secondary maximum of September, while the prominences fell off considerably both in September and November, but attained their greatest development in March and April. lanetary Tables.—An important and laborious o is being carried on by Prof. Simon Newcomb, consisting of the redetermination of the elements of all the large planets from the best and most recent observations, and of the construction of tables founded on uniform data. This involves an immense amount of computation, including the re-reduction of the older lanetary observations and the discussion of the ater ones, with a view of reducing them all to a uniform system. Another branch of this planetary work is a determination of the mass of Jupiter from the motions of Polyhymnia, and a comparison of Hansen's tables of the moon, with observed occultations since 1750. In commenting upon recent determinations of |..."; masses from the motions of comets, rof. Hall says: “The objection to deducing values of planetary masses from the motions of comets consists, I think, in the fact that apparently other forces than that of gravitation act on these bodies. As a comet approaches the sun it changes form, disintegrates, and matter is thrown off to form a tail. Until we know more of the theory of these changes, the computation of masses from the motions of comets and inferences about the resisting medium in space must be uncertain.” The Earth.-M. A. Ricco has called attention to a phenomenon that gives a striking proof of the rotundity of the earth, though it has hardly been noticed hitherto. At the Observatory of Palermo, which is 14 miles from the Mediterranean Sea and 2362 feet above its level, a great number of photographs of the sun, reflected from the surface of the water, have been taken a few minutes after rising or before setting, and they show that the diameter in the plane of reflection is less in the reflected image than in the direct. This deformity is due to the fact that the surface of the water forms a cylindrical mirror. with axis horizontal and normal to the plane of reflection: the amount of the observed flattening accords well with that demanded by theory. Saturn.—Dr. F. Terby, of Louvain, reported, on the evening of March 6, 1889, discovery of a
white . on the rings of Saturn adjacent to the shadow of the ball and similar to the white spots sometimes seen upon Jupiter. On the 12th it was again seen with an eight-inch Grubb telescope, but it was invisible on the 13th, 20th, 22d, and 23d, and on April 2. Evidence as to the real existence of this spot is extremely contradictory. Several observers have confirmed Dr. Terby's discovery, but Mr. Common was unable to see the spot with his five-foot reflector, nor could it be seen with the great Lick telescope. Prof. Hall is inclined to believe that the phenomenon is an effect of contrast. The very fine division on the outer ring of Saturn, detected with the thirty-six-inch Lick refractor early in 1888, was again seen in 1889, at a distance of about one sixth of the breadth of ring A from its outer edge. A dark shading extended inward from the new division almost to the inner edge of the ring. Prof. Holden has also noted an extremely narrow, brighter polar cap, about five seconds wide, in a direction parallel to the equator and perpendicular to this, about the width of the Cassini division at the ansae. Asaph Hall, Jr., has found from his observations of Titan a value for the mass of Saturn of 1 : 3,500-5, the sun's mass being unity. This is in close agreement with Bessel's revised value, 1: 3,502.5, and Struve's, 1 : 3498. Uranus.-At the July meeting of the Royal Astronomical Society, Mr. Tayler described certain observations of the spectrum of Uranus, made with a direct-vision spectroscope attached to the five-foot reflector at Common's observatory, Ealing. Bright flutings were detected in the red, orange, and green, and also four dark bands in the orange, green, greenish-blue, and blue, indicating that the planet is to some extent self-luminous. No solar lines were seen. But Dr. William Huggins, by help of o hy, has found evidence of their existence. o all exposure of two hours, on June 3, 1889, he obtained a spectrum in which all the principal solar lines were distinctly seen, but he was unable to distinguish any other lines, bright or dark. Neptune.—Observations of the satellite of Neptune during the past three years have shown that the plane of its orbit undergoes considerable perturbations hitherto unexplained. Prof. Newcomb and M. F. Tisserand have, independently, suggested that this may be accounted for by supposing that Neptune is slightly flattened, and that the orbit of the satellite makes an angle with the equator. Asteroids.-Following is a table of the asteroids added to the list since Oct. 25, 1888: