302 S& W. Burnham—Duplicity of the principal Star of = 1097. 
the compounds of nitrogen and oxygen appeared as usual, but 
on admitting a little hydrogen the spectrum was completely 
changed, and lines appeared, belonging to oxygen and nitrogen, 
the one or the other, or both, according to the amount of the 
gases present, and varying with the temperature and pressure. 
r and Frankland, in their experiments upon mixtures 
obs neat of otherwise unknown elements, are due simply to 
ydrogen and the gases of the air, namely, oxygen and nitrogen. 
Yale College, March 18, 1875. 
Art. XXXIIL—The Discovery of the duplicity of the principal 
Star of 2 1097; by S. W. BuRNHAM. 
Tue naked-eye star, B A. C. 2470, is given in Mensure Me 
crometrice as a wide pair, the secondary being of Struve’s 87 
magnitude. The following measures have been made :— 
Struve  (1832°1) D = 20°20 P = 312" 
Smyth  (18384°1 20-00 315-0 
Radeliffe (1863°1 20°52 3112 
Sir John Herschel subsequently noted another companion of 
the 12th magnitude at an estimated distance of 25’. A short 
time since I examined this with my 6-inch Clark refractor to 
get the position angle of the third star, which Herschel has not 
given, and perceived at once that the bright star of the group 
was itself a close double. The components are separated only 
about 07, and considerably unequal, being 6 and 7} magni- 
tudes. No suitable opportunity has since ocenrred to measure 
the angle, but the close pair and the distant companion appeared 
to be almost exactly in the same line. Taking the latest meas- 
ures of Struve’s pair, with the estimated distances and angles 
* Solar Physics, p. 530. 
