958 
were endowed with less energy than the less steep rays, required 
for a distance of 200 KM. We cannot teil, whether this assumption 
be right. but a priori it does not look improbable, that the distri- 
bution of sound over the various initial angles is not equal. For 
the noises of the battles on shore, where also very steep guns are 
used, the distribution certainly will be more regular. 
October 22¢. The SE. wind at the surface changes into a stronger 
S.-ly current, which increases up to the A-Cu-level. 
The consequences in Zealand are evident; numerous reports of 
heavy roar of cannons, according to some observers stronger than 
during the siege of Antwerp. But this propagation does not extend 
beyond + 100 KM.; then a distinct silent region is shown. It would 
again be extremely arbitrary to ascribe the sounds beyond 160 KM. 
to the influence of wind; up to the Ci.-level little variation has 
been observed in the wind-velocity, and we know that an important 
increase of the wind-velocity up to this level would be required in 
order to allow the sound to be bent back. Inversions of some im- 
portance failed further Eastward, and those in the low pressure area 
will probably have been even of less importance. The explanation 
by refraction in the higher strata, on the contrary, does not meet 
with difficulties. 
October 24. Neither the distribution of temperature nor the 
distribution of wind above our country were especially favourable 
for a propagation of sound along the surface or in the lower strata. 
The number of reports, but especially the intensity of the sound 
in Zealand, are indeed smaller than on October 22°¢. Probably the 
rather strong Southerly current, which moved above the Kastwind 
in Zealand, caused the rather numerous reports in that quarter. 
Considering the smaller number of reports from Zealand, it is evident 
that the sounds, suddenly heard on that day on the South-Holland- 
Isles and along the New Waterway, must certainly have belonged 
fo a second area of audibility around Lille, for which the distance 
again is in the neighbourhood of 160 km. 
October 28%. Probably inversions were of little importance in our 
neighbourhood. Also the increase of wind near the A-Cu-level is 
smaller than on October 22°¢, when the surface wind was SE. and 
hence the whole SW. wind might be taken as increase of wind, 
whereas in this case already at a pretty small height above the 
surface a SW. wind blows, which then increases only a little to 2 
‘and 3 km. Thus may be explained that in Zealand so little was 
heard, while at the same time the naval guns were heard from 
about 160 to 300 km. In this case the possibility that an increase 
