The offensive side of convoying may best be shown by an illustration: When a submarine tries to torpedo a convoyed ship—as submarines are now compelled to do owing to the infrequency of unconvoyed shipping—there is always a destroyer on the scene, and the chances of the destroyer's "getting" that particular submarine are correspondingly increased. The wake of a torpedo is generally seen by the destroyer's lookouts, and it gives a good line on the direction where the submarine is lying. The destroyer immediately steers a course full speed in the line shown by the wake of the torpedo and drops repeated depth charges along this course.

In a considerable proportion of cases, this proves effective, for these depth charges cause serious commotion over a considerable radius.

Surface Signs May Be Missing.
The correspondent was told of three cases in the last fortnight in which submarines were thus destroyed. In many instances, no doubt, submarines are destroyed without any visible indication above the water of their loss. Still others are badly crippled, as in the case of the damaged German Ubont which was recently interned in Spain. 