In accordance with the custom of the last two years, the department of physics of Harvard University has arranged three popular lectures, open to the public, on various topics in the field of physics which will be given on the first three Friday afternoons in May, as follows:

Friday, May 2.--"The Modern Steam Locomotive"--Professor. H. N. Davis 06, consulting engineer, U. S. Bureau of Mines since 1921.

Friday, May 9--"Vibrations on High Frequency with Application of Radiotelegraphy", with Demonstrations--Professor G. W. Pierce '01, Director of the Cruft High Tension Electrical Laboratory.

Friday, May 16--"Electricity in Illuminations"--Professor H. E. Clifford Ed. '92, Gordon McKay Professor of Electrical Engineering.

The lectures will be held in the Jefferson Physical Laboratory at 4.30 o'clock in the afternoon instead of in the evening as heretofore and will be open to the public free of charge. The lectures are considered of especial interest to school teachers and their pupils.