The defence of a line of communication ought to be arranged on the same plan as that adopted for the defence of a trade route, viz. making unceasing efforts to attack the intending assailant. Within the last few years a good deal has been written about the employment of cruisers. The favourite idea seems to be that peace-time preparation for the cruiser operations of war ought to take the form of scouting and attendance on fleets. The history of naval warfare does not corroborate this view. We need not forget Nelson's complaint of paucity of frigates: but had the number attached to his fleet been doubled, the general disposition of vessels of the class then in commission would have been virtually unaltered. At the beginning of 1805, the year of Trafalgar, we had--besides other classes--232 frigates and sloops in commission; at the beginning of 1806 we had 264. It is doubtful if forty of these were attached to fleets. It is sometimes contended that supply-carriers ought to be vessels of great speed, apparently in order that they may always keep up with the fighting ships when at sea. This, perhaps, is due to a mistaken application of the conditions of a land force on the march to those of a fleet or squadron making a voyage. In practice a land army cannot separate itself--except for a very short time--from its supplies. Its movements depend on those of its supply-train. The corresponding 'supply-train' of a fleet or squadron is in the holds and bunkers of its ships. As long as these are fairly well furnished, the ships might be hampered, and could not be assisted, by the presence of the carriers. All that is necessary is that these carriers should be at the right place at the right time, which is merely another way of saying that proper provision should be made for 'the stream of supplies and reinforcements which in terms of modern war is called communications'--the phrase being Mahan's. The efficiency of any arrangement used in war will depend largely on the experience of its working gained in time of peace. Why do we not work the direct system of supply whilst we are at peace so as to familiarise ourselves with the operations it entails before the stress of serious emergency is upon us? There are two reasons. One is, because we have used the permanent base method so long that, as usually happens in such cases, we find it difficult to form a conception of any other. The other reason is that the direct supply method is thought to be too costly. The first reason need not detain us. It is not worthy of even a few minutes' consideration. The second reason deserves full investigation.