1997PASP..109...15H

begin{tex}We present an analysis of the multiperiodic SX Phoenicis star BL Camelopardalis (GD 428). Along with 24 times of maximum light from archival data, six previously unpublished times of maximum light from photomultiplier observations and 39 new CCD observations of maximum light are reported. The new CCD observations indicate that BL Cam is a double-mode variable with a primary period of 0.0391 day, a secondary period of 0.0306 day, and a π_{1}/ π_{0} ratio of 0.783. The relation between metallicity and period ratio for large amplitude δScuti variables is examined in detail. Finally, evidence is presented that the fundamental period π_{0} has increased by 0.009 seconds in the last 20 years.