The Royal Naval Air Service plays a large part in the anti-submarine campaign. Its seaplanes are always scouting over our waters and sight enemy submarines from afar. Flying high, they can and do discover submarines navigating below the surface, and by wireless or other signals bring destroyers or other craft to the scene, where by special means submarines are destroyed. Probably gunfire is the chief means by which submarines are sent to the bottom. A German submarine may attain complete submergence from the cruising trim within about three minutes; but the time may be longer, if she has a gun mounted, wireless rigged, and other top hamper. From the awash position, in which her speed is reduced, she may submerge in about two minutes. A swift destroyer, knowing the position of such a submarine, may advance toward her, covering a nautical mile within two minutes, so that she has an excellent chance of coming within range and putting in shots with effect. Gunnery is carried to a high pitch of proficiency in the Navy, and one destroyer may be mentioned which knocked out the periscope of a German submarine at a range of over 2,000 yards with her first round. There is nothing an enemy submarine likes less than to see destroyers tearing down towards her at high speed as she is getting in her gun, withdrawing her periscope, lowering her masts—often a disguise—and filling her tanks. Moreover, complete submergence may not be a sure protection for her if she is watched, for she may be destroyed by an explosive bomb. German submarines have also learned to fear armed merchantmen, which have not seldom used their guns with effect, sometimes compelling their assailants to submerge, and so evading their attack, and sometimes by obtaining direct hits. The _Dunrobin_ in September, 1916, carried on a lively action for some minutes, hitting her assailant in the vicinity of her conning-tower with a T.N.T. shell—thereby causing an internal explosion, from which dense smoke arose—followed by three common shell, each of them making a direct hit, after which the enemy suddenly plunged at a sharp angle, evidently going to the bottom. In March, 1917, the _Bellorado_ was attacked by gunfire from a submarine, whereby her master, chief officer, and a seaman were killed, while her gunners put such shot into the assailant that she was silenced and manifestly disabled.