PHYSICS: D. L. WEBSTER 
91 
The part of this work deaHng with the general radiation of rhodium 
confirms Duane and Hunt's law exactly, and leads to a value of h of 
6.52 X 10~27 erg sec, taking e as Millikan's value 4.774 X IQ-^o esu. 
and the calcite spacing as Bragg's value 3.025 A. This lies above the 
values given by Duane and Hunt^ and Planck^ and below the values 
given by Millikan and Hull.^ If the spacing of the calcite planes is 
recomputed on the basis of MilKkan's e, it is 3.03 A, and the value of 
h is 6.53 X 10-2^ erg sec. The wave lengths and h values given with 
the graphs in this paper are computed from this value of the spacing. 
As a consequence of Duane and Hunt's law, if the spectrometer is set 
to receive one of the characteristic lines, some radiation is received as 
Fig. 1 
soon as the quantum potential is reached; but it is found that the inten- 
sity is at first only what one would expect from the general radiation at 
that wave length of no lines existed. With these rays, however, at a 
definite higher potential the intensity suddenly starts to increase more 
rapidly than before. This point therefore is the lowest potential at 
which any characteristic lines appear. 
This effect is shown in figure 1, the upper graph giving the intensity 
as a function of potential for the a doublet. The first part of the curve 
and its dotted continuation are due to general radiation alone, while the 
part to the right of the corner is due to the conbined general radiation 
