cm.), and the difficulty is found still more pronounced. Thus Rutherford[184] estimates that the total
-ray energy radiated per second by one gram of radium cannot possibly be more than
. Hence at a distance of 100 meters, where the
-rays from a gram of radium would be easily detectable, the total
-ray energy falling per second on a square millimeter of surface, the area of which is ten-thousand billion times greater than that of an atom, would be
