947 
Hence also this figure is far below 160 KM. We may remark 
here by the way, that the addition of geocoronium accelerates the 
decrease of density between the heights of 80 and 90 KM., where 
the inversion of the ray takes place, and hence adds to the shortening 
of the distance. Therefore, if indeed the silent region in the case 
of no disturbance ends at 160 KM., this is not in favour of 
WEeEGENER’s hypothesis, and we should be forced at all events to the 
conclusion, that the quantity of geocoronium ought to be much 
smaller than was assumed by WeGENER. 
c. Humpareys’ *) calculation, whereby the mixing in the lowest 
11 KM. is taken into account, but the percentage of hydrogen at 
the surface is again put equal to 0.01 °/,. The temperature was 
taken equal to 284 abs. at the surface, thence decreasing by 6° per 
KM. up to 11 KM., and thence equal to 218° abs. 
Humpnerys’ calculation has not been executed with the same 
accuracy in all details, so that his figures show a somewhat irregular 
course. Starting from his fundamental hypothesis, we find the 
following percentages of hydrogen: 
0 20 40 60 80 100 KM. 
0.01 0.04 0.7 10.7 67.7 97.3 
This again does not produce much alteration and we find in the 
same way as before: 
a He D 
34°21 85 155 
sle 90 118 
; 22°47’ 95 120 
20225? 100 Tote 
The limit of the silent region then comes at 117 K.M. for an 
angle of 25°. 
As the suppositions of WEGENER and Humpnrnys, apart from geoco- 
ronium, differ principally in two respects : the percentage of hydrogen 
at the surface and the influence of mixing in the lower 10 or 11 
KM., two further calculations were made in order to elucidate the 
influence of each of these factors : 
d. According to Wrerner’s hypotheses, but with 0.01°/, hydrogen 
as assumed by Hann and Humpureys (which means that the quantity 
of geocoronium, which at 200 KM. is put equal to that of hydrogen, 
becomes much larger). 
1) W.J. Humerreys. Bullelin Mount Weather 2, p. 66, 1909, 
