a vibrating electrometer with each one of them and they are quite heavy. If an accelerator is built so that potential radiation havarda exist on many levels of the building, and this often happens, a survey can become quite strenuous, (Laughtere) The development of a portable DC émplifier with sensitivities that range down to this region would be quite a convenience | for us. We could, had we a sufficient number of ionization chambers which we don't, use them as condenser chambers with a single electrometer. have tried. This is an approach that we Whenever possible we use propore tional counters to supplement the information obtained by ionization chambers, — . Due to the great flexibility and form of sensitivity which enn be achieved with these things, the information obtained from such instruments can be quite valuable, BF, and The long counter, the HangoneNeXibben Long Counter, is the most sensible,reliable generally accurate example of such an