724 Prof. W. H. Brage on the 
three reach it, the slope should be S5nb/p, and when four 
Anb/p. 
In the diagram (P]. XVIII.) the curve A represents the 
results obtained with an ionization chamber of depth 5 mm.; 
the ordinates represent distances from radium to gauze, and the 
abscissee the leak per second, as shown on an arbitrary scale by 
a Kelvin and White electrometer. The cone of rays had an 
angle of about 20°; 5 mmg. of radium bromide were used, 
only a small portion of which was exposed. The initial 
parabola and two straight lines joined by a short curve are 
well shown. ‘The curve B was obtained with a smaller cone, 
and plotted more closely ; it shows the straight line character 
up to short distances from the radium. Traces of more than 
one corner are to be seen in it. With the view of searching 
more closely for these corners, observations were made as 
shown in curve EK. Previous results seemed to show that 
there were three streams of nearly equal initial velocities, all 
finishing at about 3°5 to 4°5 em. from the source. Hence the 
ionization chamber was made very shallow, only 2 mm. in 
depth, and readings were taken for every half millimetre of 
approach. The results are given in the following table, and 
plotted in curve H. They are at least partially successful, 
for there is clearly a corner at Q, and probably others at 
Rand §. Also the slopes of PQ, QR, RS, ST, as drawn in 
the diagram, are in the proportion of 16, 34, 45, 65, 2. e., 
nearly as 1, 2, 3, 4. 
) 
Distance from | Leak per | Distance from Leak per | 
radium to gauze. second. | radium to gauze. second. | 
| | 
ry / 
476 262 | 401 425 | 
4°71 2°68 | 3°96 | 4°43 
4:66 2°75 | 3°91 / 4°60 
4°61 2°80 3°86 4°76 / 
4:56 2°86 | 3°81 | 4°96 / 
4°51 2°93 3°76 5°23 
4°46 3°02 3°71 5°44 
4:4] 3°15 3°66 / 5°66 
4°36 3°26 3°61 | 5°94 
4°31 3°41 3°06 | 6:17 
4°26 3°56 3°51 6°40 
4°21 3°68 3°46 6°70 
4°16 3°79 341 6°96 
411 3°92 3°36 7:26 
4°06 4:06 
| 
Since radium freed from its emanation exhibits at first only 
one disintegration process, the curve obtained from such 
