Bight—the blockading patrol—was to be the chief station of our submarines in Home waters.

Both belligerents began to design and build at once. The German went straight ahead on the one type, which, with variations, has served him throughout the War—viz., the commerce-destroying medium-sized patrol boat. To this type he later added the mine-laying submarine, and towards the end of the War he evolved the large, commerce-destroying cruiser boat.

Now, both before and during the War, we held a lead over our enemy in the matter of submarine design. That statement is confirmed by the data given by the U-boats arriving at Harwich as I write. Some time ago the British Navy prepared an antidote to a design of submarine which it was thought the enemy must, by logical reasoning, soon produce as being the obvious thing for him to think of. Our antidote has not yet had a chance to be used, as it was only recently that the German designers got to that stage in their reasoning.

But what did we build? Well, we did not want commerce destroyers at least; such work as the cutting of the Turkish communications in the Sea of Marmora and the sinking of transports in the Baltic could be done by our ordinary E boats. But we did want mine-layers, and we built those. What else? Well, I must branch off into a dissertation on submarines generally.

A submarine may be any kind of surface vessel, with the advantage added to her of being able to dive. She need not necessarily be a diving boat with a few torpedo tubes and a couple of guns. She may be anything. A surface ship can only be one thing; you cannot have a cruiser-monitor or a destroyer-battleship. But a submarine may be two things at once; and a submarine can, as a result, act unsupported. Take the case of a scouting submarine. What is the alternative? If we had no scouting submarines we would have had to keep a ring of destroyers out to watch the Bight. Those destroyers might, being out near the enemy's coast, be attacked by enemy cruisers, so that it would be essential to keep our cruisers out in support. Then if the enemy brought out—and so on—up to the final result of our battle fleet being continuously at sea, which would have been not only unnecessary wear and tear on the big ships, but a good opportunity for the U-boats if they had cared to take a chance. Take the case of the submarine mine-layer. She has the great advantage, to begin with, of not only getting to her position unseen, but of being able to lay her unpleasant cargo down unsuspected and unobserved. Then, again, she does not need a supporting force to follow her in case she meets with trouble. She does not look on a big enemy ship as a trouble, should one interfere with her; she would rather describe the big ship as a "gift." She is open to the usual anti-submarine methods, and can be dealt with by destroyers, seaplanes, and so on; but if she succumbs to their attacks—well, that is another submarine gone, but it might have been a big surface ship.

By the nature of the German strategy our lines of design were indicated. The chief type we needed were scouts—in other words, patrol boats. We built these in considerable numbers, for the several types of patrol boats we diverged into were capable of doing any of several things. They could do the Heligoland Bight patrol, attacking the enemy if met with, and reporting to the C.-in-C. what they saw on their patrols; they could go out into the Atlantic to hunt U-boats on the traffic lanes, or they could go to the Mediterranean to work in the Adriatic. They were the general-utility craft of the Submarine Navy.

The mine-layers were of the patrol boat type, getting larger as the War went on, but always with the torpedo-tubes (reduced in number) built into them to allow them to become normal submarines when a chance arose.

In the early part of the War there were some additions to the Submarine Flotillas in the shape of V-W and F boats of 500 submerged tonnage. These were experiments by the Admiralty in building boats of foreign design, drawings being used of the Laurenti and Fiat firms. After these boats had been tried and their best points copied into our own designs, the standard British ideas were reverted to for war construction. The building of these boats served its purpose in giving us an insight into the lines upon which other nations were working, but foreign designs were not continued owing to the better performances of our own boats.

The G and J class were patrol boats—the G's being of 975 ton submerged displacement, and so larger and with more beam than the E boats; the J's were 19-knot boats of 1820 tons submerged, and marked a great advance in the big-submarine type. The year 1915 gave us the addition of a number of E class, while the G's began to join up with the Flotillas in November of that year. The first J boat commissioned in the spring of 1916.

The H class were small patrol boats of American design—a design later enlarged and improved in England. The L boats were enlarged and improved E's, and are probably the finest patrol submarines in existence.

The 4th August 1916 saw the commissioning of a boat which was a revolution in submarine design. This was the first K boat. This class was designed for the expected Fleet action; their qualities were to be—that they should have several knots in hand over the speed of the Battle Fleet, that they should be seaworthy and able to cruise with the Fleet, and that they should have the necessary submarine qualities to enable them to deal with the High Sea Fleet when it should be met. These qualities they have; but it is regretted that the enemy gave them no chance of trying their luck in action. They were used on patrol to keep them from getting stale during the long wait for their "Day," and their experiences on patrol, and when at sea on the periodic occasions when the Fleet went hurrying out in reply to reported enemy activity, have given invaluable data for future construction of large and fast submarines. These boats are of 1880 tons (surface) and 2550 tons (submerged) displacement. They have a speed of slightly over 24 knots on the surface, can carry a good gun battery if required, and their hulls being low and well stream-lined, and their torpedo armament powerful, they can act both as destroyers by night or as submarines by day.

These boats have a battery capacity sufficient for a day's Fleet battle, but no more. They may be described as having great strategic speed and capacity, but small tactical radius: that is, they can get to the place where they are wanted quickly, but are circumscribed in their capabilities of remaining submerged in that spot for long, or of moving fast submerged for more than one attack without rising to recharge their batteries. In submarine design as well as in that of surface ships, you can't have everything; each type is a compromise.

At the other end of the scale we built the R boat. These were also "specialists," but of opposite qualities. Of 500 tons (submerged) they have a surface speed of about 8 knots, but a submerged speed of 14½—a speed which will probably be slightly increased by alterations. These boats only joined up in the summer of 1918, and the enemy surrendered before they had really shown what they could do. A boat of this type (they are perfectly stream-lined, and, inside, they are all battery and torpedo tubes) can jog out to her assigned area at her leisure—it is no use sending her to cut off or meet a definitely reported enemy, as she wouldn't get there in time—and once in that area she can use her diving batteries for days without having to recharge them, should she be kept down by enemy hunters, and her high submerged speed and radius make her very dangerous to any target (U-boat or otherwise) which passes within periscope range of her.

There remains the submarine monitor, which will be described in due course. I will interpolate here an account of a typical trial of a new boat, using an E boat of the early 1916 vintage as an illustration.

II