recorder and analyzer, and then by varying the gain of the amplifior and the fine pulse-helvunt adjustment on tne recorder until total absorption peairs from standards of known samma energies (Hp 293, Na ee ana cs iST) fell at the appropriate positions on the recarding paper (Fig. 2). found that this calibration was very stable, It was requiring only an occasional small adjustment in the zero-set control of the recorder to allow for variation in paper placement and ruling defects on the paper. That the equipment was essen- tially stable in the Y direction was shown by periodic checks with the 60-cycle test position of the count-rate meter and by the linearity of the decay curves on semi- logarithmic paper of the calibrated standards. vt Pulse height spectra were recorded for each sample on standard gain (3 Mev full scale) and on "high" gain-amplifier gain increased by a factor of four (0.75 Mev full scale)--in those cases where the strength of the sample allowed it. How long the taking of periodic recordings of each sample could continue after shot time before the count rate became too low for statistically significant results depended of course, on the original strength of the sample. On nearly all of the standard-gain records, a calibrated Na 22 standard source was recorded on tne same sheet in a different color ink, while on the high-gain records a 9