with a flame. The external radiation of
may then be studied by placing it in the interior cylinder of a cylindrical condenser (Fig. III.). The interior cylinder is of aluminium,
. It is brought to a potential of 500 volts. The external cylinder,
, of the condenser is of copper. It is in connection with an electrometer and piezoelectric quartz. By means of the quartz the current passing through the condenser is measured. This current is caused by the Becquerel rays that escape from the tube
, pass through the cylinder of aluminium
