ASTRONOMY. 129 



Observation of sun-spot spectra. — Professor Young mentions a some- 

 what curious observation of sun-spot spectra, which he has recently- 

 made. He finds that under high dispersion the spectrum of the darkest 

 part of the spot is not continuous, but is made up of countless fine, 

 dark lines, for the most part touching or slightly overlapping, but leav- 

 ing here and there unoccupied intervals which look like (and may be) 

 bright lines. " It seems to indicate that the principal absorption which 

 darkens the center of the sun-spot is not such as would be caused by 

 minute solid or liquid particles — by smoke or cloud, which would give 

 a continuous spectrum ; but it is a true gaseous absorption, producing 

 a veritable dark-line spectrum, in which the lines are countless and con- 

 tiguous." 



Solar activity in 1886. — According to Professor Tacchini's observa- 

 tions (Comptes Rendus, 103 : 120 ; 104 : 216), it appears that there was a 

 decided falling off in the number and size of sun-spots during the year 

 1886. In March, however, there was a considerable temporary increase ; 

 and on the 8th of May a magnificent grouj) of spots was visible in the 

 sun's northern latitude. A well-marked minimum occurred in November, 

 and rather peculiar "secondary minima" seem to have fallen in the 

 months of February, May, and August. Prominences also showed a 

 diminution in number and size compared with those seen in 1885, but 

 the fluctuations were much fewer than in the case of the spots. A par- 

 ticularly remarkable eruption was observed on March 9 and 10. 



Professor Tacchini places the last great minimum of spots in March, 

 1879, and the last maximum in February, 1884 ; if then the decrease 

 in the number of spots during the latter part of 1886 corresponds to a 

 new minimum, we shall have an interval from the last maximum of 

 only 2.8 years, whereas the mean interval is seven years. So short an 

 interval between maximum and minimum is very exceptional, for the 

 shortest known since 1750 is 4.3 years ; the longest is ten years. 



Total eclipse of the sun, August 28-29, 1886. — A party consisting of 

 Lockyer, Tacchini, Schuster, Maunder, Perry, and others, was sent out 

 by the British Government to the island of Grenada, in the West Indies, 

 to observe the total eclipse of August 28-29, 1886. A full review of 

 the results of the expedition can not be given until the detailed report 

 is ready. Preliminary accounts show that only one division of the 

 party, that with Mr. Lockyer at Green Island, failed entirely on ac- 

 count of clouds, though the observations at some of the other stations 

 were more or less interfered with. Photometric observations and pho- 

 tographs of the corona and of its spectrum were obtained, and also 

 good spectra of the prominences, showing the bright lines of highly 

 incandescent vapors. In this respect the result resembles that obtained 

 in the two previous eclipses, though it was thought possible that this 

 year, being one when sun-spots were tending to a minimum, would be 

 marked by the more continuous spectrum that bespeaks lower tempera- 

 ture. 



H. Mis. 600 9 



