00, excluding
reserves--and the improbability of producing them in Great Britain.

(2) The great depth of water in which many of them were to be moored, a
depth in which no mines had ever been successfully laid before; time
would be required to devise arrangements that would enable the mines to
be laid at such depths.

(3) The very large number of patrol craft that would be needed to force
submarines to dive into that portion of the minefield which was safe for
surface vessels and the difficulty of maintaining them at sea in bad
North Sea weather.

(4) The difficulty of preventing egress by the submarines in Norwegian
territorial waters, in which, even if mines were laid, they would have
to be moored at such a depth as not to constitute a danger to vessels on
the surface.

Shortly after the subject was broached to us we learned that the United
States Navy had devised a mine that it was expected would be
satisfactory for the purpose of the barrage. An experienced mining
officer was at once sent over by us to inspect the mine and to give to
the United States officers such assistance as was possible due to his
great knowledge of mining under war conditions.

When he arrived in the United States the mine was still in the
experimental stage, but later he reported that it promised to be
successful, and in view of the great manufacturing resources in America,
it appeared that a considerable proportion of the mines for the barrage
could be provided by the United States Navy. Our own efforts to produce
a mine suitable for very great depths were also proving successful and
anticipations as to manufacture were optimistic. Accordingly plans were
prepared for a barrage across the North Sea, which were given to Admiral
Mayo before he left England on his return to the United States. Without
seriously relaxing our mining operations in the Heligoland Bight, and
without interfering with our mine barrage on the Folkestone-Grisnez
line, we anticipated at this time that we could provide mines for our
portion of the North Sea Barrage by the time that the United States
supply of mines was in readiness to be laid.

Admiral Mayo was also furnished with papers dealing at length with our
naval policy at the time and the intended future policy, both in home
waters and abroad. Papers were given him relating to our air policy, to
the attitude of neutral countries, to the Belgian coast problem, to the
blockade, to the defence of trade (includi