to last your ships about four-and-a-half weeks.
Consequently you must have a stream of colliers running to the
place so as to arrive at intervals of not more than about thirty
days. Calculations founded on the experience of manoeuvres show
that in war time ships would require nearly three times the quantity
used in peace. It follows that, if you trebled your stock of
coal at the base and made it 30,000 tons, you would in war still
require colliers carrying that amount to arrive about every four
weeks. Picture the line of communications with the necessary
colliers on it, and see to what extent you are released from
the necessity of defending it. The bulk of other stores being
much less than that of coal, you could, no doubt, maintain a
sufficient stock of them to last through the probable duration
of the war; but, as you must keep your communications open to
ensure the arrival of your coal, it would be as easy for the
other stores to reach you as it would be for the coal itself.
Why oblige yourself to use articles kept long in store when much
fresher ones could be obtained? Therefore the maintenance of
store depots at a secondary base no more releases you from the
necessity of guarding your communications than it permits freedom
of movement to your ships.

The secondary base in time of war is conditioned as follows. If
the enemy's sphere of activity is distant from the base which
you have equipped with store-houses and fortifications, the place
cannot be of any use to you. It can, and probably will, be a
cause of additional anxiety to you, because the communications
of its garrison must still be kept open. If it is used, freedom
of movement for the ships must be given up, because they cannot
go so far from it as to be obliged to consume a considerable
fraction of their coal in reaching it and returning to their
station. The line along which your colliers proceed to it must
be effectively guarded.

Contrast this with the system of direct supply to the ships-of-war.
You choose for your flying base a position which will be as near
to the enemy's sphere of action as you choose to make it. You
can change its position in accordance with circumstances. If you
cease to use the position first chosen you need trouble yourself
no more about its special communications. You leave nothing at it
which will make it worth the enemy's while to try a dash at it.
The power of changing the flying base from one place to another
gives al