a 943 
men-of-war joined in the bombardment of the Flemish Coast, and 
12-inch guns were said to have been in action. 
And vet, in Zealand this time little was heard. So much the 
stronger were the battle-noises at great distance. The line of 160 KM. 
plays a certain part again, but that of 200 KM. likewise is clearly 
indicated. The reports from the province of Groningen give a north- 
erly origin, but evidently as far as Kampen and Dalmsholte (280 
KM. the sound of the naval guns penetrated. 
November 1st. The location of the battle is based upon corresponding 
reports from English and German sides, which place the end of the 
fighting, at which moment probably the bombardment was most 
severe, at 40 sea-miles W. of Helgoland. Also in this case there is 
no real silent region; however. if we look at the heavy sounds, 
which were frequent enough here, one sees that these are wanting 
between the circles of 118 and 175 KM. round the terminal spot of 
the battle, whereas they aye rather numerous in the province of 
North-Holland at the line of 198 KM. Hence there is sufficient 
evidence of an increased audibility beyond 160 KM. 
Concluding, we think we are allowed to say that in many of these 
cases ap increased audibility has been established near the line of 
160 AM., and that beyond this line more roar of cannons was heard 
than in the belt of 40 or 60 KM. bordered outwards by this circle. 
In none of these cases is there a clear indication of a unilateral, 
asymmetrical propagation of the sound — but only rarely the reports 
were numerous enough to allow definite conclusions in this respect. 
7. The foregoing shows clearly, in our opinion, that under the 
widely varying meteorological circumstances occurring in our country 
on the davs mentioned, there was never an indication of a silent 
region that would end as early as 114 KM. For the rest, however, 
the state of things resembles in many respects that state which von 
DEM Borne’s theory would lead one to expect. The question therefore 
arises: how is it to be explained that this theory is not verified 
quantitatively > 
We have already observed that the meteorological circumstances 
can alter little in the minimum distance. Hence nothing remains 
but a eriticism of the hypotheses about the composition of the 
atmosphere, on which Von prem Bornr’s theory is founded. 
Von prem Borne takes 280° abs. for the temperature at the surface, 
220° abs. at 12 KM. and a constant temperature from there. In 
explaining his formulae he starts from the assumption that the 
molecular weight of the air remains constant up to 12 KM. in 
61 
Proceedings Royal Acad. Amsterdam. Vol. XVIII. 
