essary to
make well-known landfalls during transit. The third is, that the
multiplication of our great ports of distribution have divided the old main
flow of trade to the Channel into a number of minor streams that cover a
much wider area and demand a greater distribution of force for effective
attack. It will be obvious that the combined effect of these considerations
is to increase still further the chances of individual vessels evading the
enemy's cruisers and to lessen the risk of dispensing with escort.

Nor are the new practical difficulties of sporadic operations on the great
routes the only arguments that minimise the value of convoys. We have also
to remember that while the number of vessels trading across the ocean has
enormously increased since 1815, it is scarcely possible, even if the
abolition of privateering prove abortive, that the number of cruisers
available for pelagic attack could exceed, or even equal, the number
employed in sailing days. This consideration, then, must also be thrown
into the scale against convoys; for it is certain that the amount of
serious operative damage which an enemy can do to our trade by pelagic
operation is mainly determined by the ratio which his available cruiser
strength bears to the volume of that trade. This aspect of the question is,
however, part of a much wider one, which concerns the relation which the
volume of our trade bears to the difficulty of its defence, and this must
be considered later.

It remains, first, to deal with the final link in the old system of
defence. The statement that the great routes were left undefended will seem
to be in opposition to a prevailing impression derived from the fact that
frigates are constantly mentioned as being "on a cruise." The assumption is
that they in effect patrolled the great routes. But this was not so, nor
did they rove the sea at will. They constituted a definite and necessary
part of the system. Though that system was founded on a distinction between
defended terminals and undefended routes, which was a real strategical
distinction, it was impossible to draw an actual line where the one sphere
began and the other ended. Outside the regularly defended areas lay a
region which, as the routes began to converge, was comparatively fertile.
In this region enemies' cruisers and their larger privateers found the mean
between risk and profit. Here too convoys, as they entered the zone, were
in their greatest danger for