1886.] NEW YORK ACADEMY OF SCIENCES. 259 



been joined with Pickering's by tlic Royiil Astronomical So- 

 ciety, in the bestowal of their gold metlal for his wedge-photo- 

 meter and the ])hotometric work done with it. The Harvard 

 photometry, and the Uranometria Oxoniensis together will carry 

 down to all time the record of the present brightness of the 

 stars. They will be especially valuable as data for determining 

 ciianges in stellar brilliancy. 



During the i)a8t ten years the number of variable stars has risen 

 from about 100 to nearly 150; and our knowledge of their periods 

 and light-curves has been greatly improved. In America, Chan- 

 dler and Sawyer, of Boston, and Parkhurst, of this city, have 

 done especially faithful work. During the ten years we have 

 had two remarkable "temporary stars," as they are called — 

 first the one which, in November, 1876, in the constellation of 

 Cygnus, blazed up from the ninth magnitude to the second and 

 then slowly faded back to its former brightness, but to a nebido^cs 

 condition, as shown by its spectrum. Then also the one which, 

 last autumn, appeared in the heart of the nebula of Andromeda as 

 of the sixth magnitude (where no star had ever been seen before), 

 slowly dwindled away, and is now beyond the reach of any exist- 

 ing telescope. Perhaps, too, we ought to mention another little 

 ninth magnitude star in Orion's club, which last December rose 

 to the sixth magnitude, and is now fading; it seems likely, how- 

 ever, from its spectrum, that this is only a new variable of long 

 period. 



As to star-spectra, a good deal of work has been done in their 

 investigation with the ordinary stellar spectroscopes by the 

 Greenwich Observatories, by Vogelat Potsdam, and by a number 

 of other observers, — work well deserving extended notice if time 

 permitted. But the application of photography to their study, first 

 by Henry Draper in this city, and by Huggins in England, is the 

 important new step. By the liberality of Mrs. Draper, and as a 

 memorial of her husband, his work is to be carried on with the 

 new photographic instrument and method just introduced by 

 Prof. Pickering at Cambridge. He is able to obtain on a single 

 plate the spectra of all the stars down to the eighth magnitude 

 in the group of the Hyades, each spectrum showing under the 

 microscope the characteristic lines quite sufficiently for classifica- 

 tion. A different instrument is also to be built with the Draper 

 fund, which will give single star-spectra on a much larger scale 

 and in fuller detail. 



During the decade, the stellar parallax has been worked at by a 

 number of observers. Old results have been confirmed or cor- 

 rected, and the number of stars whose parallax is fairly deter- 

 mined has been more than doubled. The work of Brunnow and 

 Ball in Ireland, of Gill and Elkins at the Cape of Good Hope, 



