“…We have made an attempt to extend their investigations to smaller values of s.s.d. For this purpose we converted, using the "F" factor, the depth dose data obtained by JOHNS, Epp, CORMACK, FEDORUK (1952) and by DIXON, GARRETT, MORRISON (1952) for a source-skin distance of 60 em into data for the source-skin distances used by ourselves as well as by MEREWETHER, OSBORN, WYARD (1952) Table I, columns 4 and 6, and in Table II, columns 3 and 5. As may be seen, it seems that for small areas the "F" factor may be used for all depths and for all source-skin distances between about 15 em and 100 cm without introducing any appreciable error.…”