The following is a list of dates which has been obtained since the compilation of List I in December 1963. Owing to an irreparable leak in our original counter, it became necessary to replace it with a new counter of similar design using the same shield as before. The new counter has been operated both at 500 mm Hg pressure, where it has a background of 1.7 counts/min and an NBS oxalic count of 11.4 counts/min, and at 1000 mm Hg pressure, where it has a background of 2.5 counts/min and an NBS oxalic count of 22 counts/min.