Instrumentenkunde," describes a simple apparatus, which he has devised for the purpose of registering the readings of the wedge photometer without disturbing the condition of the eye by bringing up a light to read the micrometer-head.

Herr Repsold has recently proposed a partially automatic method of recording transits. The transit is mounted so as to be virtually an equatorial, with a small motion only in hourangle near the meridian. A star just before transit is brought into the center of the field of view, and the driving-clock started, so that the star remains steadily in the same part of the field, and its position in the field may be observed with the right - ascension micrometer. Meanwhile the telescope is following the star up to the meridian, and on reaching the meridian the clock-work is automatically disconnected and a record made on the chronograph sheet.

United States Naval Observatory.-Prof. William Harkness, of the executive committee of the Transit-of-Venus Commission, has given the preliminary results of the work of that commission, which are detailed elsewhere. The great equatorial has been used in observations on the fainter satellites and double stars. The transit-circle work has been continued, as in previous years, and comets and asteroids

known as the Henry Draper Memorial has been much extended. The second annual report of the director on this work, shows that two telescopes are kept at work at the observatory, photographing stellar spectra every clear night. Four assistants are required in making the pictures, and five are employed for measurements and reductions. The report gives the mode of testing the sensitive plates. Mrs. Draper has sent to the observatory the 15- and 28-inch reflectors constructed by Dr. Draper, which are used in the above-mentioned work. In continuation of the work of examining high altitudes for the purpose of testing their suitability for astronomical purposes, Prof. Todd, of Amherst, tested some high points in Japan, whither he had gone to observe the eclipse of August, 1887. His report is favorable.

In Parts 3, 4, and 5 of vol. xviii of the “Annals" are described Mr. Parkhurst's photometric measures of the asteroids, observations made during the total lunar eclipse of Jan. 28, 1888, the photographic search for a lunar satellite, and Mr. W. H. Pickering's observations of the total solar eclipse of Aug. 29, 1886.

Yale College Observatory.-Dr. Elkin's report for 1887-'88 has been published. Heliometer observations on the parallaxes of the ten firstmagnitude stars are completed. His results are as follow:

and star occultations by the moon, and observations of stars for the Yarnall Catalogue have been kept up. Prof. Eastman began his zone work with the transit circle about October 1st. Capt. R. L. Phythian has replaced Commander Brown as Superintendent of this observatory.

A circular "Relating to the Construction of a New Naval Observatory" has been issued by the Navy Department. The plans of the proposed observatory have been completed. It will be on Government property, at Georgetown Heights, Washington, D. C., and will comprise nine buildings. 1, the main building, 69 x 307 feet, which will contain the transit-room, library, etc.; 2, the great equatorial building, 46 × 72 feet; 3, the clock-room, 18 x 20 feet; 4 and 5, observers' rooms, each 18 × 20 feet; 6 and 7, east transit-circle building and west transit-circle building, each 30 x 40 feet; 8, prime vertical building, 18 x 20; 9, boilerhouse, 45 × 54.

Harvard College Observatory.-Through the continued liberality of Mrs. Draper, the work

The value for a Canis Minoris (Procyon) above given agrees well with the mean of the values found by Auwers and Wagner. Struve found for a Aquila (Altair) a value of +0.181", and Hall's value for a Tauri (Aldebaran) was +0.102". O. Struve obtained very different parallaxes for Aldebaran and Capella, and the seven independent determinations of parallax of a Lyra which have previously been made, agree fairly well in assigning to it a parallax of about +0.17". Dr. Elkin is now engaged on a triangulation of the regions near the pole, to get fundamental places of twenty-four stars; and in connection with Dr. Gill (at the Cape of Good Hope) he will this winter observe the opposition of Iris for the determination of solar parallax.

Lick Observatory.-The Lick Observatory was formally transferred by the trustees to the regents of the University of California on June 1, 1888. Of the $750,000 left by Mr. Lick for the purpose of building the observatory and purchasing instruments, all has been expended except, it is said, about $90,000. This is the

nucleus of a fund the interest of which is to pay for the care and use of the observatory and instruments. The University of California is making efforts to increase this maintenance fund to $1,000,000. The observatory has recently issued the first volume of its publications. The contents of the volume are Mr. Lick's deeds of trust; Prof. Newcomb's report on glass for objectives; report of Mr. Burnham's work at Mount Hamilton in testing the climate for double-star work in 1879 and again in 1881; descriptions of the buildings and instruments; an account of the engineering and building at Mount Hamilton in 1880-'85; observations of the transits of Mercury in 1881, and of Venus in 1882; geological reports; meteorological observations, 1880-'85; reductiontables for Lick Observatory.

instruments. (See "Annual Cyclopædia" for 1885, page 54.)

New American Observatories.-The Denver University Observatory, of Colorado, is to be provided with new observatory buildings and a new refracting telescope with 20-inch objectglass. The telescope is to be mounted 5,000 feet above sea-level, or 800 feet higher than the great Lick telescope. Mr. H. B. Chamberlain, of Denver, is the donor.

The Dearborn Observatory, of Chicago, is being removed to Evanston (within a few miles of Chicago). It will be placed on a site 250 feet from Lake Michigan. It is expected that the 183-inch equatorial will be remounted in its new home in January, 1889.

Foreign Observatories.-The report of the Pulkowa Observatory for 1887 says that the 30

Mr. Keeler has recently shown that the seeing in winter is not especially better at the observatory than at lower elevations. At other times "the secret of the steady seeing at Mount Hamilton lies in the coast fogs. These roll in from the sea every afternoon in the summer, rising from 1,500 to 2,000 feet. They cover the hot valley, and keep the radiation from it shut in. There are no fogs in day-time, and few in winter."

The complete instrumental equipment of the observatory is as follows: equatorials of 36, 12, and 6 inches aperture, a 4-inch comet-seeker, photoheliograph, 6-inch meridian circle, declinograph, 4-inch transit and zenith telescope combined, 2-inch universal instrument, three chronographs, five independent clocks, besides controlled clocks and chronometers, minor astronomical and a good set of meteorological

inch refractor was employed by Dr. Hermann Struve in measuring those of Burnham's double stars which are only seldom measurable with the old 15-inch, together with other stars of which measures are scarce, making a working catalogue of 750 stars. Observations were also made of the fainter satellites of Saturn, and of that of Neptune. Ludwig Struve has calculated the constant of precession and the motion of the solar system in space. He obtained values not greatly different from those previously calculated.

The Royal Observatory, Greenwich, is to have a new 28-inch refractor. The glass disks have been cast by Messrs. Chance, and the lenses will be made by Sir Howard Grubb.

At the Oxford Observatory Prof. Pritchard examined for the Photographic Committee of the Royal Society two silver-on-glass mirrors

of the same aperture, but of different focal lengths. He found that mirrors, particularly those of short focal length, are comparatively unsuitable for the photographic work of charting the heavens.

At the Paris Observatory M. Loewy's new method for determining aberration and refraction is being used. The brothers Henry have continued their magnificent work in celestial photography, having taken seventy-four plates of different parts of the sky in 1887. The report of the director, Admiral Mouchez, contains an engraving of the Pleiades made up from three of the Henry protographs.

Astronomical Photography.-Prof. Pritchard, of Oxford Observatory, was encouraged by his success in determining from photographic plates the parallaxes of the components of 61 Cygni, to discuss the parallaxes of μ Cassiopeia and the pole-star. His equatorial he improved, and on each of fifty-three nights four plates were taken of μ Cassiopeia. The exposures varied from five to ten minutes. About three per cent. of the plates were injured or unsuitable for measurement. He took two impressions on the same plate, slightly moved in position. Two comparison-stars were used. The resulting parallaxes were:

From star (A) π = 0·0501′′ ± 0·027′′. (B) = 0·0211 ± 0·0235. An investigation of the results obtained by using only a few selected plates of 61 Cygni and Cassiopeia has led Prof. Pritchard to give up the laborious method used in the case of 61 Cygni, and hereafter to limit the observations to five nights in each of the four periods of the year indicated by the position of the parallactic ellipse. He hopes in this way to determine in one year the parallaxes of fifteen stars. He plans to apply this method systematically to all stars between the magnitudes 1.5 to 2.5 which are well visible at Oxford. From a discussion of the approximate parallaxes that he expects to obtain, Prof. Pritchard hopes to infer some important cosmical relations. The result of his approximate determination of the parallax of Polaris is = 0.052". A mean of all the determinations of preceding observers is, according to Maxwell Hall, π = = 0.043". From six months' observations, Prof. Pritchard has obtained the following provisional parallaxes:

a Cassiopeiæ, 0·072"±0.042".
B Cassiopeiæ, 0:187 ± 0·039.

y Cassiopeia, 0·050 ± 0·047. Isaac Roberts has taken photographs of the ring nebulæ in the Lyre (57 M. Lyre), the dumb-bell nebulæ (27 M. Vulpecula), and the fine, globular star-cluster (13 M. Herculis). In the first the ring was well shown, also the central star and nebulous matter in the interior, but there was no evidence of resolvability. The photographs seem to confirm the suspicion that the central star is variable. Photographs of the star-cluster showed prominent features not noticed by Sir J. Herschel and

VOL. XXVIII.-4 A

the Earl of Ross. All these photographs were enlarged from three to twenty-five times. Mr. Roberts calls attention to the important fact that, owing to different causes, which are not easily discernible, but may be atmospheric, chemical, and mechanical, the same area in the heavens will show, on the same exposure with similar plates, with apparently the same clearness of sky, surprising differences in the number of stars. He finds, on comparing MM. Henry's plate of the stars in Cygnus taken in 1885, with those taken by himself in 1886 and in 1887, that the number of stars in the Henry plate is 3,124; in his plate of 1886, 5,023; and in his plate of 1887, 16,206; the exposure in each case was sixty minutes. The brothers Henry have succeeded in taking a photograph of the Pleiades after an exposure of four hours, which shows very much more nebulous matter than their well-known photograph taken last year. The negative shows stars down to the seventeenth magnitude.

Photographic Chart of the Heavens.-Dr. Gill, at the Cape of Good Hope, is pushing this work in its preliminary stages with great energy. The photographic instrument is kept at work by two observers from evening twilight until dawn. The reduction of the plates from south polar distance 0° to 12.5° has been completed, and measurements are proceeding to south polar distance-30°. Derby dry plates were used with half-hour exposure, instead of an hour as previously. Dr. Gill, in a paper published by the International Committee for the Photographic Charting of the Heavens, proposes the establishment of a central bureau consisting of chief, assistants, secretaries, and a staff of measurers and computers to take the photographs and measure them and make a catalogue, the work to go on for twenty-five years, at a cost of $50,000 per annum. would require the cataloguing of 2,000,000 stars. Some astronomers object to this work as being unnecessary. It is expected that a considerable number of observatories in Europe and America will begin work on the photographic chart in 1889.

This

Solar Parallax.-Prof. William Harkness, in No. 182 of the "Astronomical Journal," gives an abstract of his paper, read before the A. A. A. S., "On the Value of the Solar Parallax deducible from American Photographs of the Last Transit of Venus." In this paper an account was given of the instruments and processes employed by the United States Transit of Venus Commission in determining the solar parallax from photographs of the transit of Venus which occurred in December, 1882. Let be the solar parallax, and 8A and 8D, respectively, the corrections to the right ascensions and declinations of Venus given by Hill's tables of that planet. Then, on the assumption that Hansen's tables of the sun are correct, there resulted from measurements of the distances between the centers of the Sun and Venus, made upon 1,475 photographs,