In a 43-inch telescope it appeared as a small, bright, nebulous star, without a nucleus. It was moving rapidly both east and south. This comet was originally discovered on Nov. 26, 1818, by the astronomer Pons, at Marseilles. It was then visible for seven weeks. Prof. Encke, of Berlin, subjected the observations to a careful investigation, and showed that the orbit was elliptical, with a period of about three and one third years. He identified the comet with the comets of 1786 I, 1795, and 1805, and predicted its return. His calculations were almost exactly fulfilled. Ordinarily it appears to have no tail. In 1848 it had two, one about 1° in length directed from the sun, and the other a little shorter, and turned toward it. At perihelion the comet passes within the orbit of Mercury, and at aphelion its distance from the sun is about equal to that of Jupiter. Investigations of the motions of this comet show that its period is steadily diminishing by about two and a half hours in every revolution. Encke's theory was that the comet, in moving through space, met with a resistance from some rare medium, which was not able to impede the greater masses of the planets. Many astronomers are inclined to doubt the existence of a resisting medium; but lately, Dr. Backlund, the Swedish astronomer, from an examination of the observations of the comet between 1871 and 1881, concludes that there is a retardation, although the amount is less than that assigned by Encke. No other comet seems to be retarded, so that if we accept the theory of a resisting medium we must imagine that it does not extend very far from the sun. The in

1843. It had a bright nucleus and short tail, but was not visible to the naked eye. Leverrier investigated its orbit, and predicted its return to perihelion on April 3, 1851. It returned within a day of the time predicted. Its perihelion distance is about 100,000,000 miles, and its aphelion distance about 500,000,000 miles.

Comet V was discovered on September 2, by E. E. Barnard, at the Lick Observatory. It was described as circular, 1' in diameter, eleventh magnitude, with a well-defined nucleus. No decided motion was observed in twenty minutes. Prof. Boss calculated the provisional elements given in the table, which show that the theoretical brightness at perihelion would be about seventy times the brightness at discovery. The same observer furnishes the following notes:

September 5. The comet has a soft but condensed light. The coma is somewhat less than 30" in diameter, and symmetrical. The condensation is very uni form toward the center, without a distinct nucleus Under illumination the central parts-some 5" in di ameter-appear as a star of 11.5 magnitude.

September 6. There is a very small nucleus of about the thirteenth magnitude.

September 10. The nebulosity is elliptical, with axes of about 40" and 60" respectively. Nuclear condensation well marked, and is, perhaps, 10" south of the center of the nebulous mass.

Comet VI was discovered by E. E. Barnard, at Lick Observatory, October 31. He describes it as having no tail, a strong central condensation, of the eleventh magnitude, or fainter; the nebulosity was 1' in mean diameter, and was much elongated.

We give the approximate elements of these comets in the following table:

1888, Aug.,

II.. 1SSS, June, 28
III.. 1888, July, 30.25
IV
20

9.84450 9.5352 9.95424

Feb. 18, Sawerthal.. Comet a, 1588 July 8, Tebbutt...

Encke's.

Aug. 7..Brooks

9.45

209° 40' 8° 23' 137° 52'

857° 46' 267° 10'

1858, Dec., 10.41 VI.. 1888, Sept., vestigations of Mr. Sherman seem to point in the same direction as those of Dr. Backlund.

Comet III was discovered by W. R. Brooks, of Geneva, N. Y., August 7. On August 10, Prof. Boss reported the comet as small and condensed, and showing, with low powers, as a star of the ninth magnitude. It had a short tail with an estimated length of 10', and of the same breadth as the head. It had already passed perihelion when discovered, and was rapidly diminishing in brightness. It was thought that observations might be made up to the October moon.

Comet IV was found at Nice Observatory on August 9. The ephemeris shows that the comet is slightly increasing in brightness. This comet is one of the short-period comets. Its last appearance was in 1880; its period is 74 years. The present is its seventh appearThis comet was first discovered by M. Faye, at the Paris Observatory, on Nov. 22,

ance.

The Sun. The minimum period for sun-spot occurrence was prolonged during the first four months of 1887. There was a sudden slight increase in the number of spots in the beginning of May, 1887. In the present eleven-year period two minima have occurred: one, from Sept. 22 to Dec. 8, 1886, and the other from January to May, 1887. Including both of these periods in the same minimum, by neglecting the interruptions at the close of 1886, then the whole minimum period includes 222 days, and the date of the minimum may be given approximately as Jan. 10, 1887. This does not refer to the absolute minimum for this elevenyear period. On Oct. 28, 1887, some faculæ, attached to a group of faint spots, are reported to have become on a sudden intensely bright, and faded again as quickly. No other change of importance occurred in the spots themselves, or in their neighborhood. Within three minutes both faculæ and spots had entirely disappeared. The magnetic instruments indicated no disturbance. There were many days in 1887 when the sun was without spots, but very rarely were faculæ entirely absent.

Saturn. Many skillful observers, among whom may be mentioned M. Trouvelot, Dr. Terby, and Mr. Elger, consider that the rings of Saturn are not stable, but are subject to continual changes. Dark masses have been observed on ring C, indentations have been seen on its inner edge, and other noticeable appearances recorded. Some astronomers have been inclined to consider that these appearances have no real existence, but that they are due to bad seeing, distorting eye-pieces, etc. Prof. Hall, in using the great Washington glass, was, we think, unable to see some of the markings drawn on the rings by Trouvelot in his wellknown picture of Saturn, as seen with a 26inch instrument. Mr. Keeler, of Lick Observatory, in the February number of the "Sidereal Messenger," in speaking of the distortion of Saturn's shadow, drawn by Trouvelot, says he had often noticed the distortion "when observing with the 12-inch equatorial, with a low power on a poor night; but it always disappeared on employing a sufficiently high power, or with improvement in the definition."

which extended in ward, diminishing in intensity, nearly to the great black division. At its inuer edge the ring was of nearly the same brightness as outside the fine division. No other markings were visible."

In the supplements to the "Pulkowa Observations," Prof. H. Struve discusses his own observations made with the 15-inch refractor in 1884-'86 on Iapetus, Titan, Rhea, and Dione, with a view to correcting the elements of these satellites and also of determining the mass and ellipticity of Saturn. Herr Struve's value of the mass of Saturn agrees closely with Bessel's, being 13,498; the sun being unity.

G. W. Hill, in the "Astronomical Journal," of July 12, 1888, discusses the motion of Hyperion and the mass of Titan. He points out the errors in the calculations of several computers, and gives as his value of the mass of Titan 14,714, the mass of the planet being unity.

Mars.-Prof. Schiaparelli's observations on Mars, made during the opposition of 1881-'82, have been published. His new map agrees in general with that drawn in 1879. There are some noticeable differences, however, these being in a region seen by a number of observers to undergo changes. The main interest of this memoir centers in the full account of the "remarkable duplication of many of the canals." Thirty duplications are recorded between December, 1881, and February, 1882. The author thinks the phenomenon is periodic, and he concludes that duplication is connected with a period corresponding to the tropical year of Mars, and depending on the martial seasons. The tendency to duplication is pointed out as showing itself in other regions of Mars. Other observers have noted this tendency. Schiaparelli thinks it impossible to deny the reality of the duplications, however difficult of explanation they may be. E. W. Maunder, in the September number of "The Observatory," in discussing Schiaparelli's observations, remarks that "it seems impossible to accept this as a description of a real objective change taking place upon the actual surface of the planet, though as a record of a subjective appearance it must be unhesitatingly received. Prof.

the air to the ground. 3. The perihelion-distances of nearly all the orbits in which these stones move were not less than 0.5 nor more than 10 time the earth's radius. The author assumes as fully proved the connection of comets with meteors, and considers therefore that the meteorites have velocities relative to the sun not greater than 1.414 nor less than 1-244 time the earth's velocity in its orbit (earth's orbital velocity 18.38 miles a second). Mr. Lockyer, in his paper read before the Royal Society, Nov. 17, 1887, gives the result of his experiments on meteorites. He examined meteoritic spectra under various conditions, particularly that of feeble temperature. He found it possible to obtain from meteorites spectra that showed the most peculiar features of almost every variety of spectrum-solar, star, nebular, and cometary. "In the spectra of nebulæ, for instance, seven lines have been detected, of which three were traced to hydrogen, three to low-temperature magnesium, and the seventh, which has not yet been traced to its originating element, has been given by the glow from the Dhurmsala meteorite. The most characteristic nebular line was identified with the low-temperature fluting of magnesium, and the unusual spectrum obtained from the comets of 1866 and 1867 was ascribed to the same cause. The changes observed in the spectrum of the great comet of 1882 were such as would correspond to the changes induced by the change of temperature in the spectrum of a meteorite; and the changes in the spectrum of Nova Cygni, and the bright lines in such a star as R. Geminorum received a similar explanation; while a very full, in parts almost perfect, reproduction of a considerable portion of the solar spectrum has been obtained by taking a composite photograph of the arc spectrum of several stony meteorites, taken at random between iron meteoric poles. These and similar observations have Jed Mr. Lockyer to regard all self-luminous bodies in the celestial spaces as composed of meteorites, or masses of meteoritic vapor produced by heat brought about by condensation of meteor-swarms due to gravity, so that the existing distinction between star, comets, and nebula rests on no physical basis. All alike are meteoritic in origin, the differences between them depending upon differences in temperature, and in the closeness of the component meteorites to one another. Nova (new stars that blaze forth suddenly) are explained as produced by the clash of meteor-streams, and most variable stars are regarded as uncondensed meteor streams. Stars with spectra like that of Alpha Orionis (Rigel) are considered not as true suns, but as mere clouds of incandescent stones; probably the first stage of meteoritic condensation. Stars with spectra of the first and second type represent the condensed swarm in its hottest stages, while spectra of Secchi's fourth type indicate an advanced stage of cooling." Objection has been

raised to Mr. Lockyer's hypothesis by M. Stanislas Meunier. He contends that the only conclusion we are as yet entitled to draw from the spectroscopic researches on meteorites is, that they are composed of the same original matter as other celestial bodies.

The Observatory of Milan has published Part II, No. VII, of its observations. This last number contains a catalogue which is supplementary to two preceding ones. The first (1874) contained the observed paths of 7,152 meteors seen in 1872; the second (1882) contained 7,602 meteors, and the present publication contains 9,627

meteors.

Solar Physics. The experiments of Prof John Trowbridge and C. C. Hutchins lead them to conclude that there is unmistakable evidence of the existence of carbon vapor in the sun, and that at the point of the sun's atmosphere where the carbon is volatilized the temperature of the sun approximates to that of the voltaic arc. An exceedingly valuable contribution to science has been made by C. C. Hutchins and E. L. Holden in regard to the meaning of the lines in the solar spectrum. They say that "The dispersion given by the apparatus in the order of spectrum in which we work is such that a single wave-length occupies on the negative a space of 1.12 millimetres. This makes the distance between lines D, and D, 6·7 millimetres. We are convinced that there is much in the whole matter of coincidences of metallic and solar lines that needs re-examination; that something more than the mere coincidences of two or three lines out of many is necessary to establish even the probability of the presence of a metal in the sun." They have examined some of the doubtful elements in the list given by Prof. Young in his book on "The Sun," and find the evidence as follows: For cadmium, there were two perfect coincidences; for lead, cerium, molybdenum, urarium, vanadi. um, there was no good evidence in favor of their existence in the sun. Among the metals whose existence in the solar atmosphere has seemed probable, their experiments seem to show that bismuth and silver were present, but that tin, potassium, and lithium were doubtful. They also furnish evidence of the existence of platinum in the sun, claiming that between wave lengths 4,250 and 4,950 to find 64 lines of platinum, 16 of which agree with solar lines.

Henry Crew has made some observations with the spectroscope on the period of the rotation of the sun. He obtained, for the mean equatorial velocity, 2·437 miles a second, which corresponds to a true period of rotation of 25 88 days. Mr. Crew thinks that, while the sun-spot layer (or photosphere, if they be the same) is accelerated in the neighborhood of the equator, the layer, which by its absorption gives rise to the Fraunhofer lines, tends to lag behind, having here a smaller angular velocity than in higher latitudes. Comparing the year 1886 with 1887, observers report that the average height of both the chromosphere and prom

inences has been constant. The prominences had decreased in number. The heights of the largest prominences were much diminished. Some preliminary investigations in regard to the surface-currents of the sun seem to indicate: 1. That the direction at the poles is generally vertical to the limb; 2. That there is a decided current crossing the equator, sometimes in a northerly, and at other times in the southerly direction; 3. That changes of direction occur most frequently in mid latitudes.

Spectroscopy.-Prof. Grünwald, of Prague, has propounded a theory, according to which the wave-lengths of the lines due to a certain element in a given compound are to the wavelengths due to that same element, when the first compound is combined with some further body, as the volume the element occupies in the first case is to the volume it occupies in the second. Examining the low temperature spectrum of hydrogen, he finds that the wavelengths of its several lines are just double those of the lines of the water spectrum, line for line. Similar, but less simple relationships are given for other spectra, and Prof. Grünwald concludes from them that hydrogen and oxygen are compound bodies, and are dissociated in the sun. Hydrogen is inferred to have a composition of the form Ab; of which the supposed element A is associated with the line of the corona 1474 K; and b with the 'helium' line D. Louis Bell, Fellow of Johns Hopkins University, has given, in the "American Journal of Science," a paper describing his careful determination of the wave-lengths of the Da line of sodium. The result is to increase slightly Thalen's correction of Ångström's value, the wave-length finally adopted being 5,896-08 tenth-metres. Prof. Rowland has followed this with a table of the relative wave-lengths of about 450 standard lines, based upon the above determination, and designed to be used in connection with his photographic map of the normal spectrum. R. Copeland considers that he has discovered a line in the spectrum of the Great Nebula of Orion corresponding to the place of D. He remarks that "the occurrence of this line in the spectrum of a nebula is of great interest, as affording another connecting link between gaseous nebula and the sun and stars with bright-line spectra, especially with that remarkable class of stars of which the first examples were detected by MM. Wolf and Rayet in the constellation of Cygnus." The Astronomer Royal of England, at the January, 1888, meeting of the Royal Astronomical Society, called special attention to two points of interest in the spectroscopic determinations of the motions of stars in the line of sight. One point referred to the motion of Sirius. This star has shown a complete reversal of motion since Dr. Huggins's first results. In 1868, Dr. Huggins found the motion to be 29 miles a second receding from the earth; in 1872, 18 to 22 miles a second. The Greenwich observations in 1875-'76, showed a mo

tion of 24 miles a second. Subsequent years gave the following result: 1876-'77, 12 miles; 1877-'78, 23 miles; 1879-'80, 15 miles; 1880-'81, 11 miles; 1881-'82, 2 miles; thus showing a decreasing recessional motion. In 1882-'83 the motion was 5 miles a second, approaching the earth; 1883-84, 19 miles, approaching 1884-'85, 23 miles, approaching; 1885-'86, 24 miles, approaching; 1886-'87, 1 mile approaching; and for the year 1887, 6 miles receding. These results are to be accepted with great caution, as astronomers are not yet fully satisfied that an apparent change in the displacement of the F. line indicates a real motion in the line of sight. The change of motion indicated by the above figures is very much larger than any that would appear probable from the known motion of Sirius in its orbit. The second point of interest referred to the orbital motion of Algol. The spectroscopic observations seem to show that this interesting variable is revolving about a primary, and that the system to which it belongs is, as a whole, approaching the earth. Further observations are necessary to establish anything definite. Prof. H. C. Vogel, in a communication to the Royal Prussian Academy, says that photography has been successfully employed to overcome the effect of atmospheric tremors, so noticeable in spectroscopic work investigating stellar motions. The time of exposure employed is from half an hour to two hours.

The Constant of Aberration.-Prof. Hall has published the results of his reduction of the ob. servations made in the years 1862-'67 upon a Lyra by Profs. Hubbard, Newcomb, Harkness, and himself, with the prime - vertical transit-instrument of the Naval Observatory, for the purpose of determining the constants of nutation and aberration. He obtained as the most probable value of the constant of aberration, 20:4542′′ ± 0·0144′′. This, with Michelson and Newcomb's determination of the velocity of light, gives for the solar parallax a value of 8.810"± 0·0062".

Resisting Medium.-Freiherr v. Haerdtl, a pupil of Oppolzer, lately read a paper at Kiel University on the periodic comet of Winnecke. He found no indication of any influence on the comet's motion due to a resisting medium. On the other hand, O. T. Sherman considers that the variations in the motion of Encke's comet, other than those produced by planetary attraction, are caused by a resisting medium connected with the sun, and disturbed by those forces which produce and are produced by sunspots." He considers "that the zodiacal light is intimately connected with these disturbing forces, being in fact a locus of condensation of matter driven from the sun similarly to the tail of a comet from the nucleus, and after condensation again precipitated upon the solar surface."

Catalogues. Le Verrier, on becoming Director of the Paris Observatory in 1854, planned to reobserve Lalande's catalogue of 47,390