RADIAL VELOCITY OF THE ORION NEBULA.—From the measurement of a series of spectrograms of the three brighter stars in the trapezium of Orion, Messrs. Frost and Adams have determined the radial velocity of those parts of the nebula located by these stars. Seven plates of the star θ1 Orionis (October, 1903, to February, 1904) gave a mean velocity for the nebula of +19.3 km., three plates (December, 1903, January and February, 1904), of the star Bond 640 gave 18.0 km., and one plate (March 8, 1903) of the Bond star 619 gave +14 km. The general mean was + 18.5 km., which is slightly higher than the Values obtained by previous observers, e.g. +17.7 km. obtained by Keeler in 1890–91. Surprise is expressed as to the low value determined for the last named star, as the plate measured was an exceptionally good one, but the observers hesitate to draw conclusions from the results obtained from one plate.