Now to put this theory to the proof. In the early morning of the 22d of February, 1901, Dr. Anderson, the discoverer of Nova Aurigæ, perceived that Algol had a neighbor, a star as bright as itself, which had

Spectrum of Nova Persei. (F. Ellerman, 40 in. Yerkes.) never been there before. Within twenty-four hours of its detection the newcomer rivalled Capella, and shortly after took rank as the premier star of the northern hemisphere. Its spectrum on the 22d was found at Harvard College Observatory to be like that of Rigel, a continuous one crossed by some thirty faint dark lines.