SCIENCE. 



9 



EPHEMERIS OF SWIFT'S COMET. 



The following is a continuation of Mr. Upton's Ephe- 

 meris, which he has corrected by observations made at 

 Washington up to Jan. 7, 1881. Mr. Wendell, at Har- 

 vard College Observatory, obtained an observation for 

 position on Jan. 3, and Prof. Hall is of the opinion that 

 the comet can be followed without great difficulty, even 

 after the present moon. 



EPHEMERIS — WASHINGTON MIDNIGHT. 



Jan. 11 6 



13 6 



IS 6 



17 6 



19 6 



21 6 



23. 6 



25 6 



27 6 



29. 



R. A. 



m. s. 

 o 26 

 2 52. 

 5 15 

 7 34- 

 9 51- 

 12 7. 



14 21. 



16 35- 

 18 48. 

 21 2 



31 6 23 16. . 



Washington, D. C, January 8, 



Dec. 



+ 26 



57-4 



26 



23.6 



25 



52 2 



25 



22.9 



24 



SS6 



24 



30.2 



24 



6-5 



23 



44 3 



23 



23S 



23 



40 



+ 22 



45.8 



W. 



c. w. 



ECLIPSE OF THE SUN. 



The partial eclipse of the Sun which occurred on De- 

 cember 31, 1880, was observed with the spectroscope at 

 my private observatory. 



For this purpose, the instrument was so adjusted that 

 it would present its slit radially to the limb of the Moon ; 

 and the C line was placed in the centre of the field, in 

 order to see any solar protuberance that might be at the 

 place of observation. 



At about the time of greatest obscuration, the slit was 

 directed on the Moon's limb outside of the Sun, at some 

 distance from its western cusp. Although the limb of 

 the Moon was absolutely invisible in the telescope out- 

 side of the Sun, as ascertained before, yet, the presence 

 of the satellite was immediately made known in the 

 spectroscope, where it gave a very distinct broad grayish 

 band spectrum, running along the brighter spectrum of 

 the vicinity of the Sun. 



The phenomenon became more apparent the nearer the 

 slit was moved towards the Sun, and it vanished from 

 sight when it was at a distance estimated at 3 or 4 min- 

 utes from the solar limb. 



As the eclipse drew nearer the end, the phenomenon 

 became less and less conspicuous on the western side, 

 and at about 9 o'clock it had almost entirely ceased. 



An unsuccessful attempt was made to observe the 

 phenomenon taking place at the point of last contact, 

 when the Moon's limb left that of the Sun. For this 

 purpose the slit of the instrument was placed radially to 

 the point of emergence. But either because no phenom- 

 enon was perceptible, or perhaps rather because the slit 

 was not exactly at the right place, nothing was seen. 



If the dull spectrum obtained when the slit of the spec- 

 troscope was placed in the immediate vicinity of the Sun 

 was due only to the solar light, which is reflected by our 

 atmosphere, it is plain that this spectrum would have 

 been as bright on the Moon as it was outside of it, since 

 the terrestrial atmosphere lies as necessarily between the 

 observer and the Moon as it does between us and the 

 Sun, and therefore no dark ■ band spectrum could have 

 been seen. But as it was visible, it must be inferred that 

 besides the spectrum given off by the solar light reflected 

 by our atmosphere, there must have been some other 

 light, either emitted or reflected, coming from a point 

 situated beyond the Moon, which reinforced the spectrum 

 given off by the solar light reflected by our atmosphere. 



This hgh-, undoubtedly, cm be no o'ther than that of 

 the solar atmosphere, or Corona, visible during total 

 eclipses of the Sun. 



If this reasoning is sound, the conclusions to be drawn 

 from these observations are that the Corona, or at least 



traces of it, was visible during this partial eclipse, and 

 that it was much brighter in the northwest equatorial 

 regions than it was in the East ; and, furthermore, that in 

 the West it was less and less brilliant as it was observed 

 northward, until it was completely invisible in the north- 

 ern regions of the Sun. L. Trouvelot. 

 Cambridge, December 31, 1880. 



JUPITER. 



Observations of the Great Red Spot. 



Having devoted most of my observing time this year 

 to the phenomena? of Jupiter, I would respectfully sub- 

 mit a few observations of the great red spot, situated in 

 the south temperate zone ot the planet. 



Up to December 14, (the last observation on account 

 of cloudy weather,) I have observed forty transits of the 

 red spot across the central meridian. Thirty-four of these 

 have been complete transits, i. e., the preceding end the 

 middle and the following end being observed. 



The following table contains twenty-nine of these 

 transits and is given in Greenwich mean time. The first, 

 third and fifth columns give the observed time of passage 

 of the preceding end, the middle and the following end 

 of the spot. 



Columns two, four and six, contain the times by which 

 each portion of the spot preceded the passage ot an as- 

 sumed meridian that has a rotation period ot 9' 1 55 111 

 27. s o8 (an ephemeris of the transits of this meridian has 

 been pub'ished at intervals in the English Mechanic, by 

 Herr A. Marth ot the Royal Astronomical Society, and 

 is corrected tor parallax, velocity of light and phase). 



The last column (7) contains the duration of transit 

 in minutes, that is, the interval between the passage of 

 the P and F ends. 



Transit of Jupiter's Great Red Spot. 



Greenwich m. t. 



August 30 



September 9 



14- 



" 16. 



October 



November 1. 



4--- 

 S... 



^ 1 23 

 December 2.. 



S — 

 7— 



' 9— 



»4r- 



1 



2 



3 



4 



5 



G 



7 





d 





a 





c 









'5) C 



ding 

 eridi 



ilt of 

 die. 



M .5 

 = 13 

 '■5 S 



it of 

 nd. 



ding 

 endi 



ion 

 sit. 



C » 



Prece 

 Ass'd M 



S3 



8* 



£W 



8 2 





PL, 



H 



Pre 

 Ass'd ] 



5 ■ ■ 

 H 



1 Prt 

 1 Ass'd 





in. 



k. m. 



h. m. 



h. m. 



h. m. 



7)1. 



m. 



17 21.9 



1 34-7 



17 45-4 



I IX. 2 



18 11. 4 



45-2 



49-5 



15 38 9 



1 26.6 



16 02.4 



1 03.1 



16 26.4 



39-i 



47-5 







15 14.4 



55-4 



















! 16 19.4 



1 27.2 



16 49.4 



57-2 



17 11.4 



35-2 



52.0 



1 18 01.4 



1 22.0 



18 24. c) 



58.5 



18 50.4 



33-o 



49.0 



j 18 45.0 



1 19. J 



19 09.7 



54-9 



'9 32-3 



32.2 



47-3 



: 16 155 



1 .6.5 



16 40.1 



5'-9 



17 03.9 



28.1 



484 



'7 5 T -5 



1 17-3 



18 19.5 



49-3 



18 44.0 



24.9 



52-5 



13 44-3 



1 15.2 



14 12.0 



47-5 



14 39.0 



20.5 



54-7 



12 48-7 



i 15-1 



13 16.7 



47.1 



13 44-7 



19.1 



56.0 



18 32.2 



1 17.7 



19 00.2 



49-7 



19 27.0 



22.9 



54.8 



1 16 00.7 



1 16.7 



16 26.7 



SO- 7 



16 55-7 



21.7 



55.0 



1 '3 3»-2 



1 13.8 



13 57-2 



47.8 



14 23.0 



22.0 



51.8 



14 16.0 



1 10.5 



14 40.0 



46-5 



15 03.8 



22.7 



47.8 







16 17.2 

 14 34-7 



46.2 

 38.3 









14 04.9 



1 08 1 



'4 i6-5 



HYs 



5V.6 







12 01. 



39-9 



12 25.2 



157 





14 52.0 



1 °3-3 



15 16.7 



38.5 



15 43-1 



12.2 



51. 1 



16 30.2 



1 02.2 



16 55.0 



37-5 



17 19.4 



13.0 



49.2 



12 20.1 



1 03.2 



12 42.9 



40.4 



13 11. a 



12. 1 



51.1 



13 03.2 



1 02.8 



13 28.0 



40.0 



S3 54-8 



11. 4 



5'-4 



14 44.2 



59-i 



15 08.7 



34-6 



I 5 34-° 



9-4 



49 .8 



16 25.9 



54-8 



16 47.2 



33-5 



17 15-5 



5-2 



49 6 



12 18.2 



53-4 



12 39-5 



32.1 



13 06.2 



5-4 



48.0 



14 42.9 



49-S 



15 02.2 



30.2 



15 27.9 



4-5 



45-'"> 



12 12.9 



48.1 



12 32.2 



28.8 



12 57.2 



3-8 



44-3 



13 46-5 



Si.o 



14 10. 



28.5 









15 24-9 



50.2 



15 49-3 



25.8 



16 12.7 



2-4 



47-8 



14 33-2 



49-3 



14 56.0 



26.5 



15 21.4 



1.1 



48.2 



The above table shows that the red spot varies consid- 

 erably in length. These variations are shown in the last 

 column, marked "Duration of Transit." 



