d Swiss
neutrality. Flight Lieutenant Sippe's log, which has been quoted above,
certainly gives some ground for this contention. The British Foreign
Office, in their reply, said that instructions had been given to the
British aviators not to fly over Swiss territory, that it was not their
intention to do so, and that it had been the belief of the Foreign
Office that they had not done so. The British Government assured the
Swiss Government that if Swiss neutrality had been violated it had been
by inadvertence, and expressed their great regret that any British
aeroplanes should have flown over any part of Swiss territory. At the
same time the British Government were careful to point out that the
International Congress of 1910 had failed to come to any agreement as to
the recognition of territory in the air, and that Great Britain's desire
to respect the wishes of the Swiss Government should not be taken as an
admission 'that Great Britain is necessarily bound in all cases to
respect a doctrine which, however it may be viewed by herself, is not
accepted and may not be acted upon by other Powers'. This point of law
has since been settled. The International Air Convention of 1921, which
has been signed by the Allied Powers, sets forth in its first article
'that every Power has complete and exclusive sovereignty over the air
space above its territory'.

The fourth raid into enemy territory, this time by seaplanes, was
carried out on Christmas Day of 1914. How deeply the threat of the
Zeppelins had impressed the public imagination and the minds of those
who were responsible for the Royal Naval Air Service may be seen by
this--that all four naval raids were directed against Zeppelin sheds.
This fourth raid, though it did not succeed in destroying any German
airship, achieved some useful observation, and had the incidental
advantage that it brought the navy into conflict with Zeppelins, and
diminished the portentous respect in which they had been held. Two naval
officers, famous by their achievements in the war--Commodore R. J. B.
Keyes and Commodore R. Y. Tyrwhitt--were in command of the supporting
force. Two light cruisers, with eight destroyers of the Third Flotilla,
sailed from Harwich for the Bight of Heligoland at 5.0 a.m. on Thursday,
the 24th of December, escorting the three seaplane-carriers, each with
three seaplanes aboard. The air was clear and the sea calm, but it was
bitterly cold. The _Arethusa_, preceded by a scr