Prof. Pritchard lays stress upon the fact that each plate must be considered as carrying with it its own scale; and, due regard being paid to the unavoidable though slight variations of scale in the different plates, he is of opinion that in this delicate class of work photography will give as accurate results as any other known method. The nebula No. 1180 of Herschel's "General Catalogue" has been photographed by Mr. Roberts in England, and by the Henry Brothers in Paris. The latter made their negative on Jan. 27, 1887, giving it an exposure of two hours, and obtaining an image extending 25' from east to west, and 15′ from north to south, with a nebulous star, or condensation, a little detached toward the south. During such long exposures as this it is necessary to guard against displacements of the images upon the sensitive plate, arising from changes in the refraction due to the earth's diurnal motion. Dr. Dryer has investigated the magnitude of these displacements, and finds that in latitude 50° north, with a perfect clock, and an accurately adjusted instrument, they will not exceed 0.5" (and may therefore be neglected) in the case of an equatorial star moving from 27" east to 27 west of the meridian, or in the case of a star of +25° declination moving from 39 east to 39 west of the meridian. Prof. E. C. Pickering has recently published his first annual report on the photographic study of stellar spectra at the Harvard College Observatory, made with funds provided by Mrs. Draper as a memorial to her husband, the late Dr. Henry Draper. The results already obtained are so encouraging that Mrs. Draper has decided to extend the original plan of the work sufficiently to embrace a complete discussion of the constitution and conditions of the stars as revealed by their spectra, so far as present scientific methods permit. In order to reach all parts of the sky, it is expected that a station will be established in the southern hemisphere. The investigations already undertaken extend only to declination -24°, and include a catalogue of the spectra of all stars of the sixth magnitude and brighter, a more extensive catalogue of spectra of stars brighter than the eighth magnitude, and a detailed study of the spectra of the bright stars. Three telescopes have been used in the work: an 8-inch Voigtländer photographic lens refigured by Alvan Clark & Sons, Dr. Draper's 11-inch photographic lens, and the 15-inch refractor of the Harvard Observatory. The spectra have been produced by returning to Fraunhofer's method of placing a large prism in front of the object-glass. The spectrum of a star formed in that way is extremely narrow when the telescope is driven by clock-work in the usual manner, but it may be broadened as much as is desired by giving the telescope a speed slightly different from that of the earth. The negatives were subsequently enlarged; and a specimen print is given of part of the spectrum of Pollux on a scale that would separate H and K by nine

tenths of an inch. In a comparatively short space it shows nearly 150 lines with remarkable clearness. Several points of interest have been already brought out by Prof. Pickering's work. A photograph of a Cygni, taken Nov. 26, 1886, shows the Hline double, its two components having a difference in wave-length of about one ten-millionth of a millimetre. A photograph of o Ceti shows the lines G and h bright, as are also four of the ultra-violet lines characteristic of spectra of the first type. The Hand Klines in this spectrum are dark, showing that they probably do not belong to that series of lines. The star near x1 Orionis, discovered by Gore in December, 1885, gives a similar spectrum, which affords additional evidence that it is a variable of the same class as o Ceti. Spectra of Sirius show a large number of faint lines, besides the well-known broad lines. Progress is reported in the various investigations that are contemplated, namely: 1. Catalogue of spectra of bright stars. 2. Catalogue of spectra of faint stars. 3. Detailed study of the spectra of the brighter stars. 4. Faint stellar spectra. 5. Absorption spectra. 6. Wavelengths. Mrs. Draper has decided to send to Cambridge a 28-inch reflector and its mounting, and the remarkably perfect 15-inch mirror constructed by Dr. Draper and used by him in making his photograph of the moon.

The literature respecting the use of photography in astronomy has recently been enriched by articles written by Mr. A. A. Common; Dr. David Gill, Astronomer Royal at the Cape of Good Hope; Prof. E. S. Holden, Director of the Lick Observatory; Admiral Mouchez, Director of the Paris Observatory; M. G. Rayet, Director of the Bordeaux Observatory; Otto Struve, Director of the Pulkowa Observatory; and Prof. C. A. Young, of the Princeton Observatory. Some of these articles are mainly historical, others are theoretical and practical, and still others are of a more popular character. Among the historical articles those by M. Rayet, in the "Bulletin Astronomique," are particularly noteworthy on account of their completeness and accuracy.

The Paris International Astrophotographic Congress.-In compliance with the request of Admiral Mouchez, an International Congress of Astronomers was called in April by the French Academy of Sciences, to take steps to obtain a photographic chart of the heavens upon the co-operative plan so successfully carried out by the German Astronomische Gesellschaft in their zone observations. The Congress was opened at the Paris Observatory on April 16, by M. Flourens, Minister of Foreign Affairs of the French Government, and addresses were made by M. Bertrand, the eminent mathematician, by Admiral Mouchez, Director of the Paris Observatory, and by Prof. Struve, Director of the Pulkowa Observatory. Admiral Mouchez was chosen honorary president; Struve, president; Auwers, Christie and Faye, vice-presidents; Bakhuyzen and Tisserand,

Observatories in the United States.-At the Naval Observatory in Washington the 26-inch equatorial has been used by Prof. Hall in observations for stellar parallax, and also in observations of satellites, of double stars, and of Saturn. The transit-circle work has been continued as in former years, and comets and asteroids have been observed with the 9-6inch equatorial. Prof. Frisby has been engaged upon a revision of Yarnall's catalogue. The facilities for testing chronometers have been improved, and the time-service has recently been considerably extended. About 200 "Gardner clocks are automatically corrected daily by a signal from the observatory, and time-balls are dropped at New York, Philadelphia, Baltimore, Washington, Hampton Roads, Savannah, and New Orleans. For the erection of a new observatory upon the site near Washington purchased in 1880, Congress has appropriated $100,000, with the provision that the cost of the whole work shall not exceed $400,000. The plans for the new buildings are now being prepared.

The latest report of the Director of the Harvard College Observatory, at present available, was submitted to the visiting committee Dec. 7, 1886. The extensive series of photometric observations has been continued, with gratifying success. Stellar photography is now receiving considerable attention, and interesting results have been obtained, to which reference has elsewhere been made. The financial resources have recently been greatly increased. The Paine bequest, half of which, about $164,000, is now available, has been added to the endowment of the observatory; and the Boyden fund of over $230,000-which was left for the purpose of making observations "at such an elevation as to be free, so far as practicable, from the hindrances to accurate observations, which occur in the observatories now existing, owing to atmospheric influences"-has been transferred to the President and Fellows of Harvard College, so that the researches Mr. Boyden had in view may be carried out under the administration of the observatory. Prof. Pickering has already occupied, during the past summer, a high station in Colorado for experimental purposes, and intends eventually to establish an observatory in the southern hemisphere, where a series of photographic observations will be carried on supplementary to similar work at Cambridge.

The report of the Dearborn Observatory of Chicago for 1885 and 1886 has lately been issued. It contains a list of nebula discovered there by Prof. T. H. Safford in 1866-'68; papers on the motion of the lunar apsides, and on the companion of Sirius by Prof. E. Colbert; and an illustrated paper on the physical aspect of Jupiter, a catalogue of 209 new double stars, and a description of a printing chronograph, by Prof. G. W. Hough. The lawsuit respecting the ownership of the instruments has been decided in favor of the observatory.

The first of the publications of the Morrison Observatory, Glasgow, Mo., is a well-printed volume of 111 pages, giving an account of the founding of the observatory, with a full description of the building and instruments, and the observations in detail. The instruments consist, chiefly, of a 124-inch Clark equatorial, and a 6-inch Troughton and Simms meridian circle, similar in plan to the meridian circle of the Harvard Observatory. Observations of double stars, of planets, comets, and occultations by the moon have been made by the director, Prof. C. W. Pritchett, assisted by Prof. H. S. Pritchett and C. W. Pritchett, Jr.; and as a preliminary work the geographical co-ordinates of the meridian circle were determined. The volume contains several drawings of the observatory, and sketches of Saturn and of comets.

Prof. Stone has devoted the 26-inch refractor of the McCormick Observatory mainly to the study of nebula; an especial feature of his work being the determination of accurate positions of all the nebulæ north of 30° south declination, which are condensed at the center and as bright as the fourteenth magnitude. The great nebula of Orion has been repeatedly examined, for the purpose of determining the relative brightness of the various condensations composing it, and thus of furnishing means of detecting any change that may take place in them. Prof. Stone speaks highly of the electric illumination, which he has applied to the equatorial.

The Washburn Observatory, which was left without a director upon Prof. Holden's resignation in the winter of 1885, was placed temporarily under the charge of Prof. John E. Davies, on July 1, 1886, and Prof. Davies has now been succeeded by Prof. G. C. Comstock, who served as assistant in the observatory to both Prof. Holden and his predecessor, Prof. Watson. The fifth volume of publications, giving an account of the work accomplished down to April 1, 1887, has been issued by Prof. Davies. With the meridian circle a series of observations has been made for the determination of the latitude, and a discussion of that co-ordinate is given by Mr. Updegraff. A list of stars has also been observed in declination, with this instrument. The 15-inch equatorial has been used for measuring double stars and for observations of Sappho (80) and of comet 1887 II. Miss Lamb contributes a useful index to certain stars contained in various Greenwich catalogues.

The 36-inch lenses of the great refractor of the Lick Observatory were safely transported across the continent, and were deposited in the vaults of the Lick Observatory on Dec. 27, 1886. The safe transportation was a matter of great moment to the trustees. lenses were wrapped separately in fifteen or twenty thicknesses of soft cotton cloth, and were put into separate wooden boxes lined with felt. No nails were used near the glasses,

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and the boxes were made to fit the latter in shape. These boxes were inclosed in two others of steel, each nearly cubical, and packed with hair. Each steel box was then inclosed in another steel box, the inner sides of which were covered with spiral springs, and both boxes were made air-tight and water tight and placed in outer chests packed with asbestus to render them fire-proof. They were then suspended by pivots in strong wooden frames, with means for turning one-quarter round every day during the journey. This was in order to prevent any molecular disarrangement in the glasses, and to avoid the danger of polarization, through the jarring of the train. The great 75-foot dome is in place and works well. It revolves with a longitudinal pressure of 225 pounds, so that the hydraulic machinery provided is almost unnecessary. Work upon the mounting, which is still in the hands of Messrs. Warner and Swasey, is progressing favorably.

The new observatory of Bucknell University, Lewisburg, Pa., was finished early in 1887. It is provided with a 10-inch Clark equatorial, and a 3-inch transit instrument. Creighton College, at Omaha, also has a new observatory, with a 5-inch equatorial and a 3-inch transit. An exchange of longitude-signals was made with the Naval Observatory, Washington, in August, 1887.

The Solar Parallax.-The report of the committee appointed to superintend the arrangements for the British expeditions to observe the transit of Venus in 1882, together with the report of Mr. Stone, who had charge of the reductions, has recently been published as a Treasury document. Expeditions were sent from England to Jamaica, Barbadoes, Bermuda, Cape of Good Hope, Madagascar, New Zealand, and Brisbane, Australia; and the observers were successful at all these stations except Brisbane, where the sky was cloudy. The British committee were not satisfied with their photographic work in 1874, and for various reasons they decided to rely entirely upon contact observations in 1882. From the observations of external contact at ingress, Mr. Stone has obtained a parallax of 8760"±0.122"; from those of internal contact at ingress, 8-8230023"; from those of internal contact at egress, 8·855′′ ± 0·036′′; and from those of external contact at egress, 8-953"± 0.048". The most probable combined result he considers to be 8.832′′ ± 0.024", which corresponds to a mean distance of 92,560,000 250,000 miles between the earth and the sun.

The commissions of the United States and France trusted principally to photography in their schemes for observing the transit of 1882. Of the negatives obtained under the auspices of the United States Commission, after the rejection of all imperfect ones, there remained 1,571 which have been measured, and Prof. Harkness believes that the value of the solar parallax deducible from them will be obtained early in 1888. The French Commission have

measured 1,019 of their negatives, and in February, 1887, M. Bouquet de la Grye announced to the Academy of Sciences that the computations necessary for their reduction were half finished, and would probably be completed about the end of 1887.

The German Commission trusted principally to heliometers in the observations made under their direction, and Dr. Auwers has recently published a large volume containing investigations of the constants of the instruments employed; but it is not known when the resulting parallax will be obtained.

The Sun. During 1886 sun-spots were confined almost entirely to the southern hemisphere of the sun, and there was a decided decrease in their size and number, relieved only by outbursts in March and May. Faculæ and eruptions seemed to follow the spots. The prominences diminished in height and mean extent, but they were nearly equally divided between the two solar hemispheres, and the decrease was not so rapid as in the case of the spots. The Greenwich photographs, supplemented by those from Dehra Dun in India, show that for the thirty-eight days beginning Oct. 31 and ending Dec. 7, 1886, there were only seven days on which even a single spot was shown. For a rotation and a half the sun was practically free from spots. Riccò, on searching the Palermo records, finds a similar case in 1875, five years after the maximum of 1870, and nearly eight years after the minimum of 1867. He predicts that the true minimum of the eleven-year period will fall in 1890. Wolf's observations at Zürich show that the variations in the spots and in magnetic phenomena kept together in 1886 as in previous years.

An exhaustive discussion of the sun's horizontal and vertical diameters, with special reference to the alleged variations in its mean annual diameter following the period of the sunspot cycle, has been made by Dr. Auwers from the Greenwich, Washington, Oxford, and Neufchâtel meridian observations. He concludes that there is no valid reason for supposing the sun's diameter to vary, and that the apparent changes arise from insufficiently determined personal equations. He also points out that meridian observations are quite unsuited for determination of any possible ellipticity in the sun's disk, and that there is no reason to conclude from these results that such ellipticity exists. The several mean values of the sun's (assumed circular) diameter are: Greenwich, 32′ 02:37"; Washington, 32' 02:51"; Oxford, 32' 02-19"; Neufchâtel, 32' 03-27", the discordances of which are to be ascribed to instrumental or uneliminated personal peculiarities. In a second paper, Dr. Auwers discusses the apparent changes of both the horizontal and vertical diameter during the course of a year deduced from meridian observations, and he concludes that the periodic variations in the monthly value of the diameters result not from

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physical changes in the sun, but from the effect of temperature on the instruments, and from difference in the quality of the telescopic images at opposite seasons of the year. other discussion of the horizontal diameter of the sun has been made by Prof. di Legge from meridian transits of the sun observed at Campidoglio from 1874 to 1883. The mean horizontal diameter at mean distance deduced from 5,796 transits by four observers on 2,213 days is 32′ 02-38". From May, 1876, the sun's transit has been observed by projection, thus enabling two or more persons to observe simultaneously, and thereby affording exceptionally favorable opportunities for the determination of personal equation.

Prof. John Trowbridge and Mr. C. C. Hutchins have recently investigated the solar spectrum with very powerful apparatus, and they find that the alleged bright bands, upon which Dr. Henry Draper based his so-called discovery of oxygen in the sun, do not exist. They have also examined Prof. J. C. Draper's hypothesis of the coincidence of certain dark lines in the solar spectrum with the lines in the spectrum of oxygen, and find it equally destitute of any physical basis.

Total Solar Eclipse of August 19, 1887.-This eclipse excited the greatest interest throughout Europe, and will be memorable as the first during which attempts were made to observe and photograph the corona from balloons. At Berlin the totality began at 5·05 A. M., and as there were few favorable points for observation within the city, the people flocked by tens of thousands out into the open country, whither they were conveyed by special trains, steamboats, and vehicles innumerable. The principal streets of the city were more thronged from 2 to 4 A. M. than they usually are at midday, and the Tempelhof field never held a larger crowd during a grand review than at daybreak on the morning of the eclipse. Most of the people obtained only momentary glimpses of the partial phases; but those at Hoppegarten, ten miles east of Berlin, were more highly favored. There the totality was concealed only by a thin veil of clouds, through which both the chromosphere and the corona were visible; but unfortunately no skilled observers were present. While totality lasted, the darkness was so great that it was hardly possible to recognize faces at a yard's distance.

In Russia, quite unprecedented preparations were made for the occasion, and, had the weather been favorable, this eclipse would have been observed and investigated there in the most thorough manner. An intelligent taste for scientific work is very widely spread among educated Russians, and their enthusiasm on this occasion may be imagined from the sale in Moscow alone of 145,000 glasses and 400,000 descriptive pamphlets. Enlightened by this surprising quantity of popular literature, the Russians of all classes flocked in great numbers to many points of observation. For

the first time in Russia, an excellent service of cheap excursion - trains was organized, with traveling comforts such as are only to be had on the great trunk-lines. Even the Grand Duke Constantine, who selected Tver as his point of view, did not disdain to travel by a special train of this class on the Nicholas Railway. During the night preceding the eclipse, about 300 persons went to Klin from St. Petersburg, and about 600 more from Moscow. The Physical Society of St. Petersburg distributed papers, with directions for amateur observations, to all passengers in the special train on the Moscow line, but the weather turned out so badly that probably not one of the blanks was filled out by the disappointed enthusiasts. Among the visitors to Russia were many distinguished foreign astronomers, all of whom were received with the utmost kindness, and assisted in every possible way.

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The central line of the eclipse first struck the earth at a point 53 miles west-northwest of Leipsic, in latitude 51° 38′ north, longitude 11° 16' east of Greenwich, where the sun was just rising. From there the line of totality, which was about 135 miles wide, sped across Germany, Russia, Siberia, China, and Japan, and finally left the earth at a point in the Pacific Ocean, in latitude 24° 27' north, longitude 173° 30' east., where the sun just setting. The actual distance traveled by the shadow was about 7,960 miles, and the time occupied was 2h 42m 12", whence the average rate of motion was 49 miles a minute, say fifty times that of an express train, or twice that of a shot from a modern, high-powered, rifled gun-but the speed was considerably less near the middle of the path, and greater toward its ends. The entire duration of the partial phase of the eclipse upon the earth's surface was 4" 53" 24". In Germany the sun was too low during totality for advantageous photographic and spectroscopic work, and for such observations it was necessary to go farther east. The best localities were in Eastern Siberia, about latitude 50° 30' north, longitude 112° east, but, as it was practically impossible to transport heavy instruments beyond the Ural mountains, and in the immediate neighborhood of these mountains the meteorologists thought it likely to be cloudy, nearly all the best equipped parties were concentrated between Moscow and St. Petersburg. This proved most unfortunate, for speaking generally, during the eclipse, the sky westward of the Ural mountains was overcast, while eastward it was beautifully clear. The neighborhood of Moscow and Tver, of which the meteorologists spoke highly as regards the chances of fine weather, was shrouded in clouds and mist, while Yekaterinburg, which they had comparatively condemned, was rejoicing in a clear sky. And, whereas the early morning hours, in which the eclipse took place, are more generally fine than the corresponding evening hours, it so happened that in the