40 



ASTRONOMY, PROGRESS OF, IN 1890. 



earlier half. While the mean distance of spots 



from t he equator was 5'46 in the first six months, 



it was l^vJ for the last six. A combination of 



two facts indicates the middle of the year 



as a well-defined date of sun-spot minimum. 



\ st cro ids. The annexed table shows the new 



Is ,>f i he year: 



-.'S3 has been named Clorinde; 286, Idea; 

 887, Nephthys; and 288, Glauke. 



Mars. At the opposition of Mars in 1890 

 his altitude was so low for northern observation 

 as to render abortive every effort to improve our 

 knowledge of this planet. In another respect it 

 was also unfavorable, viz., the earth's aphelion 

 and Mars's perihelion were not coincident with 

 his opposition. The duplication of his canals, 

 put forward so confidently by their alleged dis- 

 :vr. Sehiaparelli, was not visible with the 36- 

 inch refractor of Lick Observatory, nor with other 

 large telescopes, and their existence is not gen- 

 erally credited among astronomers. At Mount 

 Wilson, where the great observatory for the 40- 

 inch lens is to be erected, seven photographs of 

 the planet were taken on April 9 between 22 h 

 UK! 23 h 41 m Greenwich mean time; and 

 seven more on April 10, between 23 h 20 m and 23 h 

 i he same face of the planet being presented 

 to the earth in both cases. Distinct and identi- 

 fiable -pot-, and markings are shown in all the 

 fourteen pictures, but on those of the latter date 

 a considerable accession to the white spot sur- 

 rounding the south pole is shown. It is, says Prof. 

 \V. II. Pickering, in Payne's "Sidereal Messen- 

 for June. 1890, surprisingly large, amount- 

 ing to a I unit 25,000,000 square miles. He makes 

 no mention of the duplication of the planet's 

 canals having been seen on any of the plates. 



Sat ii rn. The unique observation of an eclipse 

 of the satellite .Japetus by the shadows of the 

 globe, the crape ring, and the bright ring of Sat- 

 urn was made with the 12-inch telescope of Lick 

 Observatory by Harnard on Nov. 1, 1889. The 

 phenomenon was expected, and he was prepared 

 for the work, with, fortunately, a clear sky. The 

 -atellit,- was first seen to emerge from the shadow 

 of tin- globe. p:iss into the semi-shadow of the 

 crape riii-, anil finally disappear in the shadow 

 of the inner bright ring, when approaching day- 

 light prevented further observation. The dimi- 

 nution of brightness of the satellite while in 

 t In- shadow of the crape or gauze ring was easily 

 ippan-nt. and confirmed the latter's translu- 

 cencjr, which fact has long been received. But 

 the shadow of the bright ring was as dense as 

 any op ;M| ue body eould east, a:j much so, indeed, 

 as was i |, fl t. of the planet itself, and this tends to 

 disprove the theory that it is made up of an in- 

 finite number of satellites. And the fact that 



both edges of both the bright rings are as clean 

 cut and as sharply defined as the limb of the 

 planet is another argument against the satellite 

 hypothesis. Mr. Lockyer claims to have ob- 

 tained some photographic evidence of the exist- 

 ence of bright lines in the spectrum of Saturn, 

 but Dr. Huggins saw no lines save those given 

 by ordinary sunlight. 



Jupiter and his Satellites. The great 

 red spot, floating, probably, in the atmosphere 

 of Jupiter, which for a dozen years has been 

 under observation, is still visible, though from 

 the planet's low altitude at this year's opposition, 

 it is an extremely difficult object even with the 

 largest telescopes. Spots of several varieties 

 pale-red, white, and black appear on his disk. 

 Recently a black one has made its appearance on 

 his southern equatorial belt, which, like the 

 "great red spot," has a motion of translation in 

 such direction and at such rate that one has oc- 

 culted the other. A. Stanley Williams, who has 

 directed attention to this interesting phenom- 

 enon, calculates that the black spot, if it remains 

 visible and progresses uniformly, will be in con- 

 junction with the following (east) end of the red 

 spot on July 29, with the center on Aug. 28, and 

 with the preceding (west) end on Sept. 27, thus 

 requiring two months to pass over or under the 

 red spot. 



Two of his satellites the third occasionally, 

 the fourth very rarely traverse Jupiter's disk as 

 black objects. A striking instance, observed at 

 the Warner Observatory, occurred on the even- 

 ing of July 21, 1890, when the third satellite and 

 its shadow were both on his disk simultaneously, 

 the satellite being, if possible, more densely 

 black than its shadow. It usually traverses as 

 an object with brightness so nearly equal that of 

 the planet as to be hardly discernible. No satis- 

 factory explanation of this phenomenon has been 

 given, as the sun shines alike on both disks, and, 

 if the reflective powers of both planet and satel- 

 lite are the same, as they generally seem to be, 

 the satellite while on the planet's. disk ought not 

 to be visible except when superimposed on one 

 of his belts. 



Zodiacal Light. In No. 2,976 of the "As- 

 tronomische Nachrichten," Prof. Arthur Searle, 

 of Harvard College Observatory, has a paper on 

 this theme, it being a summary of what is to 

 appear in extenso in Vol. XIX,' Part II, of the 

 " Annals " of the observatory. It contains the 

 records of this phenomenon for the past fifty 

 years. The three main topics to which attention 

 is called are : 1, the permanence of the ordinary 

 western zodiacal light ; 2, the normal distribution 

 of light in the Zodiac and its vicinity, which 

 evidently affects all observations of the fainter 

 portions at greater elongation ; 3, the phenom- 

 enon of a feeble maximum of light in opposition 

 to the sun, commonly known as the Gregenschein. 

 A daily record kept since 1877 shows that the 

 zodiacal light must be considered as a permanent 

 phenomenon, subject to only slight variations 

 apart from atmospheric causes. This concurs 

 with the writer's conclusions, resulting from 

 many years of observation, that the oft-repeated 

 statement of wavy motion seen in the zodiacal 

 light is without foundation. The same applies 

 also to the flickering motion, similar to the 

 " merry dancers " in the Aurora Borealis, imag- 



