Comets.—Popular Astronomy for February contains a photograph by Prof. G. van Biesbroeck of Wilk's comet taken on Dec. 31, 1929. The tail extends as a narrow ribbon to the edge of the plate 1°36′ from the nucleus. There are fainter tails, about 40′ long, on each side of it. There is a bright circular coma, some 4′ in diameter, with a fainter border. On Jan. 22 the tail lagged 5° or 6° behind the prolongation of the line from the sun to the comet.