AMERICAN JOURNAL OF SCIENCE. 
[THIRD SERIES,] 
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AR?, XXXVI.—Spectroscopic Notes; by Professor C. A. 
OUNG, Princeton, N. J. 
For the past few months I have been examining the spectra 
of sun-spots with great care, and ‘with an instrument of high 
Aigpersion. 
_ the spectroscope employed consists of a comet-seeker of five 
Mehes aperture and about forty-eight inches focal length, used 
both as collimator and view-telescope after Littrow’s method, 
the slit and diagonal eye-piece being as close together as it is 
the line joining them is parallel to the lines of the ruling. An 
Mstrument of this sort is incomparably more convenient than 
