C. 8, Sellack—Photography of Southern Star-clusters. 15 
Art. II]. — Photography of Southern Star-clusters; by C. §. 
SELLACK, at present Professor of Physics in the University 
of Cordoba, South America. 
In the beginning of last year, under an arrangement made 
with Mr. Rutherfurd in New York, and at the expense of some 
gentlemen from Boston, I went to Cordoba to take, in the 
seemed to be frustrated. The optical refractor of the same 
dimensions, which the observatory possesses, proved unfit for 
photographic purposes. In using only one half of the broken 
flint-lens the intensity of light would’ have been too much re- 
duced for the intended work. If anything at all was to be ac- 
os oa the two pieces of the broken lens had to be fitted 
I undertook this task with the assistance of a watchmaker in 
Cordoba, constructing an adjusting apparatus. On the circum- 
erence of each of the two segments of the lens, at the corners 0. 
the break and in the middle, were put three little metal clasps ; 
pairs of pulling and butting screws, inserted in small metal 
Pleces fastened on to the frame of the lens, worked on these 
clasps, so that with them the pieces of the lens could be lifted 
re lowered. A slight motion of the pieces of the lens parallel 
10 its surface could be effected by little wedges, the frame giv- 
ig some play to the lens. 
* Under the charge of Dr. B. A. Gould. 
