Four-color observations of early-type stars. III. M4.

Four-color measures have been made of ten blue-horizontal-branch stars in the globular cluster M4. The quantities 0 and log g have been calculated for stars with 0.00 mag < (b - Y)o < 0.12 mag, and these parameters are in accord with the (log g, 0 )-relation found for NGC 6397 and other clusters by Newell. Subject headings: globular clusters - horizontal-branch stars