A phase plot of these observations clearly distinguished the primary and secondary minima. This plot was used to identify 30 times of faintest observations during primary minimum, which are listed in Table 3. The 2.3-h interval of constant light at minimum, plus phase smearing from the long exposure times, and the accidental errors of estimation produce a large uncertainty in the times of the individual plate minima. However, the number of minima and the extended time span of the observations permit the period to be determined with reasonable precision. A least-squares solution of the 30 times of minima from Harvard plates (weight=0.05) plus the two photoelectric minima (weight=0.1) yields the following ephemeris :