955 
c. At the gunpowder explosion at Wiener-Neustadt, where the 
second area, not counting spurious observations, begins only at 
160 KM. Whether the greatest intensity of sound, which was found 
here at 210 KM.. might be ascribed to a special distribution of the 
energy of sound at the source, cannot be decided by the present writer. 
It would be possible in these cases to decide immediately whether 
the sound had made its way through the very high strata of the 
atmosphere, or had been held back in the lower 10 or 20 KML, if 
the time of propagation were known accurately. Some data about this 
point are indeed available, but often the accuracy leaves much to 
be desired. In the case of the explosion at the Eigerwand (2) the 
two statements for the immediate neighbourhood about the time of 
explosion differ by 2 minutes, and the times of propagation for distances 
of 160 to 170 KM. vary from 35 to 13 minutes. Along the orbit 
assumed bv DE Quervarn for this distance, 8 to 9 minutes would be 
required, for an orbit in case g, ascending to a height of 115 KM., 
12.5 minute. Hence the mean time of observation is in favour of 
an orbit more like that of Dr QVERVAIN, but the observation cannot 
be called decisive. 
In the case of the volcanic eruptions, investigated by Fusiwnara, 
thanks to the observations of a number of meteorological stations, 
the uncertainty of the time determinations is not so great, though 
an uncertainty of 2 minutes forms no exception. Among these 
there are at least two, that of December 7 1909 and May 25% 
L910, where at distances above 140 km. beside normal, also abnormal 
large times of propagation occur, whereas in the former case times 
of 15 and 16 minutes are stated, which would agree very well 
with a propagation through the lavers above LOO km. 
Also in the Wiener-Neustadt case at great distances times of pro- 
pagation above the normal value are mentioned. 
Hence, though the times of propagation support to a certain degree 
the applicability of the physical explanation, it cannot be denied, 
that the first impression generally pleads for a meteorological ex- 
planation; a decision however is not yet arrived at. 
So we are forced to the conclusion that in the case of Antwerp, 
where the silent region appeared so extremely regular, extraordinary 
weather-conditions have co-operated to procure an image so little 
disturbed. 
FusiwHara, as well as DE QvrrvarN and Dorr, has tried to ascribe 
the abnormal propagation of the sounds to the meteorological in- 
fluences mentioned. Unhappily these writers did not as a rule dispose 
of anything like sufficient data about the conditions in the higher 
