FLAMMARION is, no doubt, the most popular scientific writer of his generation,—a distinction he owes to the poetical quality of detached essays with which he loves to relieve his astronomical writings. These essays, though they are often prose poems of great beauty, are generally governed by scientific generalizations rather than by the poetic imagination. At times, however, Flammarion gives free rein to his imagination, as when he promoted in the scientific and unscientific world an elaborate discussion of the possibility of communicating with the possible inhabitants of the planet of Mars. He was born at Montigny-le-Roi, France, February 25th, 1842, and educated for the Church, but he has devoted his life to astronomy, writing a large number of books which have been widely read in both hemispheres. Among them are “The Plurality of Inhabited Worlds”; “Worlds, Imaginary and Real”; “The Wonders of the Heavens,” 1865; and “The World before the Creation of Man.”