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.