ASTRONOMICAL PHENOMENA AND PROGRESS. 



3. The observations by Watson and others 

 afford data for determining the extent of Ye- 

 nus's atmosphere ; while the spectroscopic ob- 

 servations indicate that on that planet, as well 

 as on the earth, the atmosphere contains a con- 

 siderable quantity of aqueous vapor. 



Prof. Alexander's Hypothesis of the Zodi- 

 acal Light. In an interesting " Statement and 

 Exposition of Certain Harmonies of the Solar 

 System," recently published by the Smith- 

 sonian Institution, Prof. Stephen Alexander, 

 of Princeton, New Jersey, proposes a new 

 theory of the zodiacal light. This mysteri- 

 ous phenomenon, the explanation of which 

 has perplexed astronomers since the time of 

 Cassini, is regarded by Prof. Alexander as a 

 terrestrial girdle, so situated that its time of 

 revolution around the earth is equal to, and in 

 the same direction with, that of the moon. 

 The author, after stating numerous objections 

 to the commonly accepted hypothesis of a solar 

 ring, and presenting a mathematical exposition 

 of the mode in which the girdle, if a terres- 

 trial appendage, may be sustained, gives the 

 following summary of special coincidences of 

 phenomena with the requirements of his the- 

 ory: 



1. That it provides a conservative force for the 

 maintenance of such an appendage. 



2. It will account for the phenomena common to 

 all the appearances of the zodiacal light, broad base 

 and all. 



3. It accounts for certain periodical changes in 

 form and intensity, etc., of the same, which seem to 

 be completed in a synodical revolution of the moon. 



4. It provides for the gegenschein in form and po- 

 sition ; and possibly also for " a lunar zodiacal light." 



6. It renders a plausible account of the fading, 

 at times, and total disappearance of the zodiacal 

 light. 



6. It accounts for the absence of a determinate 

 parallax of the girdle. 



7. It shows why, when east and west zodiacal 

 lights are visible at the same time, the middle, even, 

 of the zodiacal arch need not be wholly obscured by 

 the earth's shadow. 



8. It provides for the " pulsations." 



Asteroids. At the close of 1874 the number 

 of known asteroids was 140. In 1875 no less 

 than 17 were added to the group, bringing the 

 number up to 157. In the interesting search 

 for these diminutive planets, Dr. 0. H. F. Pe- 

 ters, of Hamilton College, New York, is now in 

 advance of all competitors. This distinguished 

 observer has detected 22, while the numbers 

 found by his industrious rivals, Luther and 

 Watson, are 20 and 17 respectively. At the 

 present rate of discovery not only must the 

 list of mythological names be exhausted at an 

 early day, but the labor of calculating the ele- 

 ments and preparing ephemerides must become 

 a serious tax upon the time and energy of com- 

 puting astronomers. The larger bodies of the 

 cluster have doubtless nearly all been observed, 

 as those recently found are mostly of the 

 twelfth or thirteenth magnitude. It is not im- 

 probable, however, in view of recent discov- 

 eries, that many more within telescopic reach 

 still remain to be detected. The magnitudes, 



dates of discovery, etc., of those found during 

 the year are as follows: 



No. 141, Lumen, was discovered on the 13th of 

 January by M. Paul Henry, of the Paris Observa- 

 tory. It is a very faint object, little brighter than a 

 star of the thirteenth magnitude. There is a re- 

 markable similarity between the elements of this as- 

 teroid and those of the 55th, Alexandra ; the com- 

 puted difference of their periods being only four 

 hours, while their inclinations and eccentricities, as 

 well as the longitudes of their nodes, are also nearly 

 the same. * 



No. 142, Polana, was first seen by Palisa, of Pola, 

 Austria, on the 28th of January. The position 

 and form - of its orbit have not yet been deter- 

 mined. Its brightness is equal to that of a star of 

 the twelfth magnitude. 



No. 143, Adria, was discovered at the same place 

 and by the same observer on the 23d of February. 

 This asteroid is also of the twelfth magnitude. Its 

 period, distance, eccentricity, and inclination, are 

 nearly equal to those of Geres, the first discovered 

 of the group. 



Nos. 144 and 145, Vibilia and Adeona, were both 

 detected by Dr. Peters, at Clinton, New York, on 

 the 4th of June. The former is of the eleventh, 

 the latter of the twelfth magnitude. The period of 

 Vibilia is 1,509 days ; that of Adeona, 1,615. 



No. 146, Lucina, was first observed by Borelly, at 

 Marseilles, on the 8th of June. It resembles a star 

 of the twelfth magnitude, and has a period of 1,627 

 days. 



No. 147, which was named Protogeneia by the dis- 

 coverer, was first seen by Dr. Schulhof, at Vienna, 

 on the night of July 10th. This minor planet is in 

 the outer section of the zone, its period being over 

 2,000 days, or about 5t years. Its orbit is very 

 nearly circular, and has an inclination of less than 

 2 to the ecliptic. 



No. 148 was discovered at Paris, August 7th, by 

 M. Prosper Henry. This minor planet has the ex- 

 traordinary inclination of 26. It resembles a star 

 of the thirteenth magnitude. 



Nos. 149-157 have not yet been named, nor have 

 their elements been computed. The names of the 

 finders, together with the dates and places of dis- 

 covery, and also the apparent magnitudes, are as 

 follows : 



Comets. The first comet observed in 1875 

 was that of Encke, detected at "Washington by 

 Prof. Holden and Paymaster Tuttle, United 

 States Navy, on the 26th of January. It was 

 also found on the following night by M. Ste- 

 phan, at Marseilles. An ephemeris of the 

 comet, calculated by Dr. von Asten, had been 

 circulated among astronomers, and the posi- 

 tion of the body when first observed was but 

 15" of arc from its predicted place. When 

 first seen, the comet's distance from the sun 

 was 142,000,000 miles, and from the earth, 

 182,000,000. Its appearance was that of an 

 extremely faint nebulosity, less than 2' in di- 



