itting a moving vessel by torpedo-fire, once she has
arrived in a position suitable for attack, lies in estimating correctly
the course and speed of the target. In the case of an ordinary cargo
ship there is little difficulty in guessing her speed, since it is
certain to be between 8 and 12 knots, and her course can be judged with
fair accuracy by the angle of her masts and funnel, or by the angle
presented by her bridge.

It will be seen, then, how easy was the problem before the German
submarine officers, and how very difficult was that set to our Navy and
our gallant Mercantile Marine.

It will not be out of place here to describe the methods which were in
force at the end of 1916 and during the first part of 1917 for affording
protection to merchant shipping approaching our coasts from the
direction of the Atlantic Ocean.

The general idea dating from the early months of the war was to disperse
trade on passage over wide tracts of ocean, in order to prevent the
successful attacks which could be so easily carried out if shipping
traversed one particular route. To carry out such a system it was
necessary to give each vessel a definite route which she should follow
from her port of departure to her port of arrival; unless this course
was adopted, successive ships would certainly be found to be following
identical, or practically identical, routes, thereby greatly increasing
the chance of attack. In the early years of the war masters of ships
were given approximate tracks, but when the unrestricted submarine
campaign came into being it became necessary to give exact routes.

The necessary orders were issued by officers stationed at various ports
at home and abroad who were designated Shipping Intelligence or
Reporting Officers. It was, of course, essential to preserve the secrecy
of the general principles governing the issue of route orders and of the
route orders themselves. For this reason each master was only informed
of the orders affecting his own ship, and was directed that such orders
should on no account fall into the hands of the enemy.

The route orders were compiled on certain principles, of which a few may
be mentioned:

(a) Certain definite positions of latitude and longitude were given
through which the ship was required to pass, and the orders were
discussed with the master of each vessel in order to ensure that they
were fully understood.

(b) Directions were given that certain localities in whic