THE POPULAR SCIENCE MONTHLY VOLUME LXXXVI JULY TO SEPTEMBER,
1915
THE SCIENTIFIC MONTHLY VOLUME I OCTOBER TO DECEMBER, 1915
EDITED BY J. McKEEN CATTELL
THE SCIENTIFIC MONTHLY ------ OCTOBER, 1915 -------------
THE EVOLUTION OF THE STARS AND THE FORMATION OF THE EARTH. II
BY DR. WILLIAM WALLACE CAMPBELL
DIRECTOR OF THE LICK OBSERVATORY, UNIVERSITY OF CALIFORNIA
THE PRINCIPLES OF SPECTROSCOPY
THUS far our description of the stellar universe has been
confined to its geometrical properties. A serious study of the
evolution of the stars must seek to determine, first of all,
what the stars really are, what their chemical constitutions
and physical conditions are; and how they are related to each
other as to their physical properties. The application of the
spectroscope has advanced our knowledge of the subject by leaps
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