36 



SCIENCE. 



stars have been discovered within the last eight yedrs, and 

 it is very probable that many new additions will be made 

 as the large refractors now in use engage in this work. 

 This list would be much extended by including stars to 

 which more distant companions have been detected, but 

 most, if not all of them, are too distant to make any phy- 

 sical relation probable, and are of very little interest. The 

 first column gives a number for reference ; the second 

 column, Struve's number; the third, the name of the 

 principal star, when found in Flamsteed or Bode ; the 

 fourth, the distance of the stars recorded by Struve ; the 

 fifth, the distance of the new star ; and sixth, the name of 

 the discoverer. 



Many of the close pairs are known to be binaries, and 

 in some cases it is probable the three stars form one 

 system. When any change has occurred, the most re- 

 cent measures of distance are given. 



ASTRONOMY. 

 swift's comet. 

 A new determination of the orbit of Swift's periodic 

 comet has just been made by Mr. Winslow Upton of the 

 U. S. Naval Observatory, based upon observations made 

 at Washington, October 25, November 23, and Decem- 

 ber 22, 1880. No assumption was made with regard to 

 the period of resolution or the eccentricity. The follow- 

 ing are the elements obtained, and communicated to the 

 Aslronom isch e Nachrich ten : 



Epoch, 1880, Oct. 25. 5 Washington mean time. 



M 357 48' 49.3" 



SI 296 41 55.4 ) 



u 106 iS 13.8 > 1880.O 



* 5 3i 3-5 ) 



<P 42 31 39-7 

 logo 0.518438 



/i 59 2 -°373" 

 The period obtained from these elements is 2189 days, 

 which confirms the fact already announced by Mr. 

 Chandler and others that the comet has made two revo- 

 lutions since its appearance in 1869. The period obtained 

 is also nearly identical with that given by Prof. Frisby in 

 " Science," which he derived from observations sepa- 

 rated by intervals of only 13 days. The comet could not 

 have been seen at its return in 1875, as the sun was be- 

 tween it and the earth, and it is probable that its next 

 return in 1886 will be unobserved for the same reason, 

 though a careful computation which shall take into ac- 

 count the perturbations of the comet due to the action of 

 the planets will be necessary to determine the question. 



Professor E. S. Holden, of the Naval Observatory at 

 Washington, has accepted the managership of the Wash- 

 burn Observatory in Madison, Wis., the position made 

 vacant by the recent death of Professor Watson. Pro- 

 fessor Holden will enter upon his duties in a few weeks. 



Astronomical Memoranda:- (Approximately com- 

 puted for Washington, O. C, Monday, January 24, 1 881 . ) 

 Sidereal time of Mean Noon. 2oh. 16m. 37s. 



Equation of time 12 29 



mean noon preceding apparent noon. 



The Sun, having passed the winter solstice, has reached 

 a declination of 19 3' south. 



The Moon reached its Last Quarter on Jan. 22d i6h., 

 or 4 A. M. of Jan. 23. 



New Moon comes on Jan. 29d. 8h., and the First 

 Quarter on Feb. jjd. 8h. On the morning of the 24th 

 the Moon crosses the meridian at about a quarter of 

 seven. 



Mer&ury, still invisible, comes into superior conjunc- 

 tion with the sun on the 26th, passes to his eastern side, 

 and becomes evening star. Mercury is in conjunction 

 with the Moon on the morning of Jan. 30. 



Venus is evening star, and throughout the month in- 

 creases her distance from the sun as she approaches the 

 earth. She follows the sun by nearly three hours and is 

 3° south of the equator. 



Mars is morning star, rising about six o'clock, and 

 slowly traveling away from the sun. 



Jupiter, evening star, crosses the meridian about half 

 past four: — R. A. oh. 53m., Dec. 4 21' north. 



Saturn also is evening star, having reached quadra- 

 ture, or halfway from opposition to conjunction, on the 

 1 2th, when he was on the meridian at six. Saturn and 

 Jupiter, it will be noticed, are still steadily approaching 

 each other. 



Uranus crosses the meridian at about 3 o'clock in the 

 morning, at a declination of 7° 21' north, and cannot 

 claim any especial attention at present. 



Neptune is in R. A. 2h. 39m ; Dec. 13 36' north. It 

 reaches quadrature on the 30th, and will be found in con- 

 junction with the Moon on — Feb. 4th. 



In the Popular Science Monthly for January, 1881, 

 Dr. Leonard Waldo gives an interesting description of 

 the method employed at the Yale Observatory, for com- 

 paring with the standards of that institution, thermom- 

 eters which have been sent there for verification by 

 physicians, instrument makers and others. He calls at- 

 tention to the fact that thermometers, even if from makers 

 of established reputation, are liable to errors much 

 greater than is commonly supposed, and he points out 

 the necessity of having such errors carefully determined. 



We learn from the Comptes Rendus that Janssen has 

 made preparations at Meudon to repeat Dr. Draper's 

 experiments on the photography of the Nebula in Orion, 

 and that for this purpose he proposes to construct upon 

 a large scale a telescope of short focus quite similar to 

 the one with which he obtained a very luminous spec- 

 trum of the Corona, in 1871. Janssen has also made 

 some experiments in photographing the chromosphere. 

 The exposure is continued so long that the solar image 

 becomes positive to the very circumference, without 

 going beyond it. The chromosphere is then shown in 

 the lorm of a dark ring with a thickness of 8" or 10". 

 He has compared positive and negative solar photographs 

 taken on the same day and with the same instrument, 

 and the measurement of the diameter shows that the 

 dark ring in question is wholly outside of the solar disk. 



Dr. Warren De La Rue has been elected a cor- 

 responding member of the Paris Academy of Sciences in 

 the section of Astronomy, and M. Sella a corresponding 

 member in the section of Mineralogy. 



The Rumford medal of the Royal Society has been 

 awarded to Dr. William Huggins for his work on celes- 

 tial spectroscopy, and the Copley medal to Prof. J. J. 

 Sylvester of Johns Hopkins University for researches in 

 pure mathematics. W. C. W. 



ECLIPSE OF THE SUN. 



To the Editor of " Science :" 



1 would like to add a sentence to the fourth paragraph 

 of my letter in last week's "SCIENCE " giving my obser- 

 vations of the recent partial eclipse of the sun. After the 

 words " solar limb " I would add, " on the eastern side 

 of the sun the phenomenon was considerably less promi- 

 nent and only visible at the time of greatest obscuration, 

 and when the slit was quite close to the sun's limb," 



L. Trouvelot. 



Cambkidge, January 12, i88r. 



