Algol

[Ar. al ghal, destructive.] (Astron.) A re mark able star in the Head of Medusa, 12° E. of Almaak. It is on the meridian the 21st of December. Nine degrees E. by N. from A. is the bright star Algenib, which with Almaak makes a perfect right angle at A., with the open part towards Ca iopeia. By means of this strikingly perfect figure, the three stars may always be recognized without the po ibility of mistaking them. A. varies from the 2d to the 4th magnitude in about 5% hours, and back again in the same time; after which it remains steadily brilliant for 24 days, when the same change occurs. Dr. Herschel attributes the variable appearance of A. to spots upon its surface, and thinks it has a motion on its axis similar to that of the sun. Matt is on.