curate elements of its orbit: Time of perihelion passage, 1898, Nov. 23.14, Greenwich mean time; from node to perihelion, 123° 22′; longitude of node, 96° 10′; inclination, 140° 19'; perihelion distance, 0.7564.

Comet 1898 J (Chase). This extremely faint comet was discovered by photography by Mr. F. L. Chase, an assistant at Yale College Observatory, who on Nov. 14 photographed the radiant of the November meteoric shower in the sickle of Leo. When the plate was developed nothing indicating a new point of light or a trail by a moving object was seen. But two weeks afterward the director, inspecting the negative, saw a minute speck slightly elongated. He requested astronomers at other observatories to inspect their plates, and the speck was found at the same place. When the region was examined with one of our great telescopes the mysterious object was identified as a comet. The shortness of the trail was accounted for by the slow motion of the comet and the short exposure, combined with its extreme faintness. From observations made on Nov. 14, 23, and 25, and Dec. 5, Prof. Möller has computed the following orbital elements: Time of perihelion passage, 1898, Sept. 19.65, Berlin mean time; node to perihelion, 4° 23′ 9.2"; longitude of node, 95° 47' 0.2"; inclination of orbit, 22° 28′ 25.2"; longitude of perihelion distance = q. 0.357918. These elements indicate that the orbit is a parabola.

Comet A 1899 (Swift) was discovered by Dr. Lewis Swift, director of the Lowe Observatory, Echo Mountain, California, on the evening of March 3. It was the brightest and most interesting comet that has appeared since the great comet of 1882. It had an interesting history while under observation, which was nearly four months. For full particulars the reader is referred to the Astronomical Journal, No. 464, where a double head and double nucleus are represented and fitful variations of brilliance are described. This variation in brilliance was a new feature in cometary astronomy. The discoverer from its subsequent behavior has reason to believe that a sudden outburst occurred just prior to its discovery, rendering it visible to the naked eye. At this time a phenomenon was seen which could not be seen the next evening nor at any subsequent evening, and which never has been seen appended to any comet. The bright coma visible to the naked eye was centrally superimposed on another very much the larger and of unimagined faintness, the marginal demarcation of the two being sharply defined. The following parabolic elements have been computed: Time of perihelion passage, April 13.0148; node to perihelion, 8° 48′52′′; longitude of node, 25° 0′ 55′′; inclination, 146° 15′ 48′′; logarithm of perihelion distance, 9.51311.

Comet B 1899: Tuttle's of 1858 — Mechain's Comet of 1790.-This interesting periodic comet was rediscovered by Dr. Wolf on March 5, 1899. It has a period of 13.7 years. It remained unobserved from 1790 to 1858. Its period is the longest of all the short-period comets.

Comet C 1899 (Holmes) = Comet III 1893.This was rediscovered, June 10, by Perrine at the Lick Observatory with the 36-inch telescope, in which it appeared not brighter than a star of the sixteenth magnitude. This is its first return since its first discovery by Holmes in 1893.

Comet D 1899 (Tempel's) = Comet II 1873.This short-period comet of six years was also rediscovered by Perrine on May 7, almost exactly at the place computed for it by Prof. Schulhof, the error being only 2' of arc.

The elements of Comet E 1898 (Perrine) resemble those of the Comets of 1684, 1785 I, Comet B 1898, and Pons's comet of 1812 Comet PonsBrooks of 1884. These facts strongly indicate that they all belong to the same family, although only the latter is periodic. The elements of the bright comet discovered by Prof. Brooks, as stated above, bear a strong resemblance to that of 1881 IV, although Dr. Stechert has computed for it a period of not less than one hundred thousand years. For comparison the elements of both are subjoined:

Variable Stars.-For three hundred years it has been known that Beta Persei (Algol or Demon star) varied periodically through nearly two magnitudes; also that Omicron Ceti (Mira the Wonderful) varied from the third magnitude to invisibility, going through all its changes in about eleven months. Many others, as now known, are at their maxima visible to the unassisted eye, but at their minima are beyond the reach of ordinary telescopes. Many theories have been advanced to account for their variability. The number of these now known amounts to more than a thousand. As amateurs can engage profitably in the work, no telescope being required, the list is increasing rapidly. In several particulars Algol is the most interesting, as the theory to account for its behavior is recognized by all astronomers as correct-viz., that it has a dark companion revolving round it, the plane of whose orbit is coincident with our line of sight, which periodically eclipses it. If this theory be true, then the bright component must alternately approach and recede from our solar system. The spectroscope has settled that question in the affirmative, giving the following data: Diameter of Algol, 1,000,000 miles; diameter of companion, 800,000 miles; distance between them, 3,000,000 miles; velocity of companion, 55 miles a second.

The shortest known variable is U Pegasi, changing in 5h 35m. Nova Auriga, when discov ered, appeared as an ordinary star of the fifth magnitude, but soon began to decline rapidly in brightness, until it reached about the seventeenth magnitude, being a difficult object in the great Lick telescope. It has a remarkable spectrum, showing many bright narrow lines and broad dark bands. Later it increased to the tenth magnitude, and is now a nebulous star. Examining the Draper memorial photographs, Mrs. Fleming, of Harvard College Observatory, discovered a new star in Sagittarius, which was first of the fifth magnitude, and therefore easily visible to the naked eye, but by March, 1899, it had declined to the tenth. The spectrum resembles those of many other variables, many of the bright lines being due to hydrogen.

No so great advance in astronomy has been made as in the discovery and classification of

Nebula. In four years of the five that Dr. Lewis Swift has been director of the Lowe Observatory, at Echo Mountain, California, he has discovered and catalogued 350 new nebulæ. Some of these are very interesting, and deserve thorough investigation with the spectroscope and the largest telescopes. Special attention is drawn to a few, as follows:

One which he calls a nebulous nebula, in right ascension 23h 29m, declination south 36° 29', has the appearance of a central elongated nebula, with sharp outline, centrally superimposed on another very much the larger and of unimagined faintness. It is probably the only one in the heavens that bears any resemblance to it, and raises the question whether there can be any connection between the two, if two there are. Astronomers are acquainted with several nebulous stars-that is, a star in the center of a nebulous atmosphere-but a nebula in the center of a nebulous atmosphere is a novelty. One in right ascension Oh 46m 458, declination south 35° 0.5', presents the curious aspect of a double nebulous Uranus. Two others, which he calls hair-line nebulæ, resembles, except in color, a short piece of horsehair. They are doubtless disk nebulæ, their thin edges being presented exactly to our line of sight. Their places for A. D. 1900 are right ascension 3h 31m, declination south 34° 47', and right ascension 5h 29m 20s, declination south 36° 28'.

Prof. Herbert A. Howe, director of the Chamberlain Observatory, University Park, Colorado, has recently discovered 22 new ones while obtaining micrometrical places of some previously discovered.

Dr. De Lisle Stewart has 46 novæ on photograph plates, taken with the Bruce photographic telescope at the Harvard Observatory station, Peru, in the latter part of 1898. The group is between right ascension 3h 10m and 3h 50m, and declination south 49° 50′ and 55° 40'. Only two appear in Dreyer's New General Catalogue of Nebula-viz., 1311 and 1356. There are several nebulous regions in the celestial vault that suggest the idea that they may be offshoots from one, or at least are connected together, the connecting links being invisible from faintness and distance. Isaac Roberts has lately reproduced a photograph of No. 2239, between right ascension 6h 24m and 6h 23m and north declination 4° 24.8′ and 5° 56.5' in the constellation Monoceros, with an exposure of 2h 45m, a depiction of nebulosity, extending like a cloud, but broken up into wisps, streamers, and curdling masses densely dotted with stars on its surface and the surrounding region. Several remarkable black tortuous rifts meander through the nebulosity, their margins sharply delineated.

Hind's variable nebula is the only well-authenticated instance of a nebula varying in brightness, somewhat analogous to variable stars. It is in Taurus, and is No. 1555 of the catalogue of nebulæ. The following observations were made with the 40-inch telescope of the Yerkes Observatory by Dr. Barnard: When discovered by Prof. Hind, of England, many years ago this nebula was conspicuous in an ordinary telescope, but in 1868 it had vanished from the largest telescopes. Mr. Burnham saw it as a very faint nebula, in 1890, in the 36-inch telescope at the Lick Observatory. In February, 1895, it was an easy object, but it had vanished the following September. On Sept. 28, 1897, it could be detected at good intervals of seeing, but with extremest difficulty, with the great Yerkes telescope. Dr. Scheiner, with an exposure of seven and a

half hours, obtained a good photograph of the spectrum of the great nebula in Andromeda from F to H. A comparison between this and the solar spectrum disclosed a surprising agreement between them. No trace of bright lines (a sure indication of the presence of gas) was present, so that the interstellar space in the nebula is not apparently occupied by gaseous matter. Th doctor calls, attention to the analogy between th Andromeda nebula and the Milky Way. T streams and irregularities of the latter he gards as of special structure, instead of a r system. The ground for this view is the f that all ring nebulæ give gaseous spectra contrast with the spiral nebula.

Dr. J. E. Keeler, director of the Lick Obs tory, on the night of Dec. 12, 1898, observer Orion nebula with the spectroscope attach the 36-inch telescope. The slit was first 1 on the nebulosity surrounding the star 734). The night being hazy, only a sing was visible, identified as HB. The slit w placed on the Huyghenian region near t pezium, which showed the usual spectru and the second nebular line (a) = 49 about equally bright, but the chief line (a was several times brighter than either. tensity of the spectrum was then dimi contracting the vertical aperture of th scope, the resolving power remaining u When the brightness was sufficiently r and the second line disappeared, the ch line alone being visible. In other wo sufficiently feeble spectrum the Hẞ lin visible in one part of the nebula, a line alone in another part. The docto the result inexplicable on physiolog and thinks it can only be due to r in the spectrum of the nebula itself Recent observations of the star varies from the second magnitude in eleven months) by Prof. Camp Mills spectrograph attached to tl scope at the Lick Observatory, star is retrograding from us at miles a second. This result wa the dark lines only, as some of show considerable displacement let. He was unable to perceive green line of hydrogen, yet th members glowed with unexpect absence of the lower radiatio anomaly of the most pronou accounted for by the divers hydrogen spectrum in nebulæ stars.

Comets. In 1898 ten co one more than ever before r Oct. 20 three only were dis two of these were expected.

Comet I 1898 (Brooks).-" was discovered by William Observatory, Geneva, N. Y the constellation Draco, i 35m 10s, declination north scopic comet it was large ble with a 3-inch telescop moon. For a while afte posed to be a return o' 1881 IV, so similar wer Further observations, c evidence that it was m therefore was a visito first and last time. Si ever, leads strongly they belong to the s ing are the latest, and

4

4

t

le

an

to

ion

ugh

that

•хсер

year,

es.

all also

vill not

e 1900, herefore as is the birthday til 1904. expedition generosity r the imme

of the Chabot with the aid out his work of observation ampbell's camp

The unusual strial surroundwas ascribed to neric dust. The

e had been prond tube in case of taken by the latter erson lens, in which ed by a new device, s limb, and also the corona, equal to 21 upon the same plate, complished. By this made for the extreme rona, which has always of great value may be

variable stars. The number now known is a hundred times greater than were known fifty years ago. But the most surprising and least expected is that many stars in several clusters vary, some during short periods and in wide limits. The literature of the subject is extensive. After the fact became known a systematic search by photography was made by Mr. S. I. Bailey at the Harvard Observatory at Arequipa, Peru, which resulted in the discovery of those mentioned below. The whole number of stars examined in the several clusters was 19,050, of which 509 were variable, or 1 variable to 37. This ratio, however, varies greatly in different clusters. While in Messier there are 13, the splendid naked-eye cluster in Hercules shows but 2 variables, or only 1 in 500. Messier 3 showed 132 in 900, or 1 in 7. No cause has been assigned for these extraordinary phenomena that meets with general acceptance. Prof. E. C. Pickering has compiled a table giving the number of variables in 23 clusters, which is published in Popular Astronomy for November, 1898, of which the following are the most remarkable: New General Catalogue 5272 Messier 3, 132 are variables; New General Catalogue 5839 Omega cluster 125; New General Catalogue 5904 Messier 5, 85; New General Catalogue 7078= Messier 15, 51, are variables. The Omega Centauri cluster, just visible without a telescope, surpasses in number of stars in a given area all others known. Its position is right ascension 13h 26m 468, declination south 46° 47'. Although it is much less than some others in extent, yet 8,000 stars have been counted on a photograph plate, but the number actually visible is very much greater. The periods of 106 of the 125 variables in the Centauri cluster have been determined; 98 have periods less than twenty-four hours. The longest is four hundred and seventy-five days, the shortest six hours and eleven minutes. The largest range in variation is about five magnitudes, and no star has been included whose light changes do not amount to half a magnitude. In one star whose period is fourteen hours and eight minutes, the rise from minimum to maximum, a change of two magnitudes, takes place in one hour. Eleven of the clusters investigated have 11,980 stars and 462 variables, or 1 in 26.

Double Stars.-A large number of the naked eye stars are found, when examined by the telescope, to be double or triple. Those that revolve around each other are called binaries, of which Castor is a familiar example. From 1877 the period of this interesting binary was considered to be one thousand and one years; but this theory has been completely upset by the fact that since 1887 the two components have been steadily approaching each other. Prof. Doberck, of HongKong Observatory, has recently computed a new orbit from all available observations. He makes the time of perihelion passage A. D. 1948.86, and the period only 318.23 years.

The line must be sharply drawn between telescopic and spectroscopic doubles. A star may be telescopically double and not be a binary, one star happening to be almost exactly behind the other. Not until orbital motion is detected beyond all doubt can the star be pronounced a binary. On the other hand, a spectroscopic double is assuredly a binary, for its orbital motion is what determines it to be a binary double. A spectroscopic double never can be seen double by any telescope, so close together are the components. When the components of such a pair revolve around each other, their orbital plane being coincident with our line of sight, the visible

star (the other supposed to be dark) must alternately approach the Earth and recede from it by the attraction of the dark one. It is this reversal of the motion of light that the spectroscope takes cognizance of. Several such spectroscopic doubles have been lately discovered, the latest find being the pole star. This polar pilot has a minute star quite close to it visible in small telescopes, but there is no reason_to suppose that they are physically connected. Polaris (as the pole star is called) is a spectroscopic binary, lately discovered to be such by Prof. W. W. Campbell, of Lick Observatory, and its duplicity has been fully confirmed by Edwin B. Frost, at Yerkes Observatory, whose observations and measurements tally almost exactly with those of Prof. Campbell. The latter is of the opinion that it is a ternary system instead of a binary-that is, the system is composed of one bright naked-eye star and two dark ones, which make a revolution around the bright one in a little more than three days. The spectroscope has proved that the pole star is moving toward the Earth at the rate of 9 miles a second. Although Polaris is approaching the Earth, yet its velocity is variable. During two days it is approaching our system at the mean rate of 14 kilometres a second, and during the next two days but 8 kilometres. This variable motion is ascertained by the displacement of the lines in the bright star's spectrum. When any star is approaching the Earth its spectral lines are moved slightly toward the violet, but if it is receding the same lines are moved toward the red end of the spectrum. The amount of displacement gives the velocity. If the velocity of a star is uniform, whether to or from the Earth, this affords positive evidence that the star is not a binary with their orbital planes coincident or nearly so with our line of sight. The spectroscope takes no cognizance of a binary star if its motion is perpendicular to our line of sight.

The photographic determination of the motion of a star in the line of sight by the spectroscope is one of the marvels of photo-spectroscopy, which, owing to more rapid plates, can now be obtained by an hour's exposure. The plate and the companion spectrum of a terrestrial source are placed side by side, and the measure of the displacement of the two spectra is then made with the microscope and micrometer. M. Deslandres juxtaposed a terrestrial spectrum with that of Alpha Auriga, and found that the displacement of the lines toward the red corresponded to a velocity of recession of 43 kilometres a second. For the dog star (Sirius) the increase of distance was 18 kilometres a second. Gamma Pegasi was found to be approaching the Earth at the rate of 3 kilometres a second. Beta Auriga showed a doubling of the lines, first detected by Prof. Pickering (proving that the star is a spectroscopic double, which no te'escope is able to divide), which indicates velocities of 100 kilometres a second, or a little more than 62 miles.

In the progress of the work of a spectrographic determination of stellar motion to and from our system several other instances of rapid motion were detected. From four plates of the spectrum of Eta Cephei a mean result was obtained showing a velocity of approach of nearly 87 kilometres a second, and four plates of the brighter component of Zeta Herculis give a velocity, also of approach, of 70.3 kilometres a second. Belopolski's result for the latter star is 70 kilometres. These results, however, are somewhat reduced when corrected for the motion of

the solar system in space-nearly toward Alpha Lyræ, according to Prof. Newcomb.

All stars, including our Sun, which is also a star, are in motion. To us they appear to move very slowly, which is owing to their great distance, whereas in many instances the motion is exceedingly rapid. Hitherto the most rapid known was 1830 Groombridge, called the " runaway star." A very interesting star in this respect has recently been discovered in connection with Prof. Capteyn's work on the Cape of Good Hope photographic Durchmusterung. It is of the eighth magnitude, in right ascension 5h 6m 40s, declination south 44° 58.2'. It has a proper motion of 9" of arc, exceeding that of 1830 Groombridge by about 12". Its rapidity of motion would indicate that it may have a large parallax, and prove it to be our nearest stellar neighbor. The circle of the sky, like all circles, contains 1,296,000", which, divided by 9, gives 144,000, the time required to complete the circle of the sky. The number of miles an hour which such a motion implies depends on the star's distance, which is unknown.

Prizes. The fifth Watson gold medal has been awarded by the American National Academy of Sciences to Dr. David Gill, astronomer royal at the Cape of Good Hope, the value of whose labors in astronomy is everywhere appreciated. The Laland prize of the French Academy of Sciences was awarded to Dr. S. C. Chandler, editor of Gould's Astronomical Journal, for contributions to astronomy. The Damoisean prize was bestowed on Prof. G. W. Hill, of Washington; the Valtz prize, on M. P. Colon, of Madagascar; the Janssen prize, on M. Belopolsky, of the Imperial Observatory of St. Petersburg. The Bruce gold medal was awarded to Dr. Auwers for various kinds of astronomical work, but especially for largely contributing to the determination of the solar parallax.

Variation of Latitude.-Dr. S. C. Chandler frequently publishes a paper in his Astronomical Journal on the variation of latitude and its cause. He contends that recent observations tend strongly to confirm the truth of his hypothesis that the axis of rotation of the Earth is not at the pole itself, but within it, and that, instead of being stationary, it describes a small ellipse with axes 0.30" and 0.08" in a year, its major axis lying along a meridian 45° to the east of Greenwich. Astronomers are about equally divided as to the truth of the hypothesis.

End of the Century.-The year A. D. 1900 is the last one of the nineteenth century, and not, as many suppose, the first of the twentieth, and as it closes a remarkable century, and is of itself a remarkable year also, it seems advisable to explain why it is not the beginning of the next century, and also why it is a remarkable year. It must be borne in mind that the year of Christ's birth was A. D. 1, the previous year being B. C. 1, there having been no year 0. Therefore, supposing he was born, as we reckon time, on Jan. 1, A. D. 1, and as it requires one hundred years to make a century, it is plainly evident that the first century ended at midnight of Dec. 31, A. D. 100. Immediately after, Jan. 1, A. D. 101, the second century began, and in like manner the third began Jan. 1, A. D. 201, and the twentieth will begin Jan. 1, A. D. 1901, nineteen centuries not having been completed until midnight of Dec. 31, A. D. 1900. Nineteen hundred is divisible by 4, without a remainder, and yet 1900 will not be a leap year. The rule for calculating leap years, briefly told, is as follows: All common years divisible by 4 and centennial years by 400,

The year

without remainders, are leap years. 1900, being a centennial year, but not divisible by 400, is a common year, the like of which has not happened in one hundred years. If the year consisted of an exact number of days, no leap year would be necessary. Also, if its length was exactly three hundred and sixty-five days and six hours, a leap year once in four years would keep the same seasons to the same months forever as they now exist, winter never occurring in July and August. For convenience we call the year three hundred and sixty-five days and six hours, while it is only three hundred and sixty-five days five hours forty-eight minutes and forty-six seconds, an annual difference of eleven minutes and fourteen seconds, which in four years amounts to forty-four minutes and fifty-six seconds, so that at every leap year we are adding forty-four minutes and fifty-six seconds too much, which in a hundred years amounts to eighteen hours forty-three minutes and twenty seconds, or more than three fourths of a day. By calling each centennial year a common year too much would be dropped by five hours sixteen minutes and forty seconds, or nearly a quarter of a day; therefore each fourth centennial is called a leap year, the extra day being dropped from the other three, which produces an almost exact correction, the error amounting to but one day in thirtysix hundred years.

This is according to the Gregorian calendar, a correction of the Julian calendar, which provided for the leap years but not for the centennials which are not divisible by 400. Some countries were slow in adopting the Gregorian calendar, notably England, and Russia has not yet adopted it, though an effort is being made to do so at the beginning of the twentieth century. At the time this calendar was adopted in England an error of eleven days had accrued, which had to be dropped, and this accounts for the celebration of Washington's birthday on Feb. 22, although he was born on the 11th, as reckoned at that time. All our Presidents, with the single exception of Jefferson, were elected in a leap year, and the President to be elected in 1900 will also be elected in a common year; but this will not again happen until A. D. 2100, which, like 1900, will be divisible by 4 but not by 400. It therefore follows that a person born on Feb. 29 (as is the case with the writer) enjoyed his last birthday in 1896, and the next will not occur until 1904.

Eclipse Expedition. The eclipse expedition to India was made possible by the generosity of Mr. W. M. Pierson, and was under the immediate charge of Mr. C. Burckhalter, of the Chabot Observatory, at Oakland, Cal., who, with the aid of two or three volunteers, carried out his work with perfect success. His place of observation was only two miles from Prof. Campbell's camp of the Lick Observatory party. The unusual brightness of the sky and terrestrial surroundings, which was very marked, was ascribed to the presence of much atmospheric dust. The Pierson photographic telescope had been provided with a duplicate lens and tube in case of accidents. The photographs taken by the latter were good, but those of the Pierson lens, in which the exposures were controlled by a new device, show the finest at the Sun's limb, and also the greatest extension of the corona, equal to 2 diameters of the Moon, all upon the same plate, a thing never before accomplished. By this method, if allowance be made for the extreme brightness of the inner corona, which has always been underrated, results of great value may be secured in future eclipses.