In the present state of the science, they say, a submarine attacking a ship is bound to come to the surface to take bearings or else to betray her presence by optic tube or periscope. With the new invention that has been evolved on the _Vernon_, the sighting of a submarine entails her almost certain destruction. Sighting is said to be now practically certain, though it is not to the public benefit that the means which will be employed should be stated, as the principle has other and varied uses. The experiments were made with H.M. torpedo-boat destroyer _Starfish_. On the starboard side certain plates had been strengthened, and above there was a crutch upon which worked a spar or outrigger torpedo. A spar-torpedo is really a movable observation mine. In the present instance it consisted of a stout pole some 42 feet in length, at the end of which was an explosive charge of 32 lbs. of wet gun-cotton, explodable by an electric current by the crew in the boat. Normally this boom stows inboard and forward, but on going into action it is slung out well forward and immersed in the water in the proper moment. This immersion carries the boom end downward and aft, and it is exploded directly the submarine is past. The idea is that the speed of the destroyer will carry her past the centre of the explosion before the full effects reach her. Her strengthened plates add to her safety, and it is thought that in any case destroyers are too light and “cork-light” to be seriously affected. As for the submarine below the waves, the men of the _Vernon_ make out a pitiable case for her. She will experience the full force of the terrific concussion. Within from 50 feet to 100 feet or more of the centre of explosion, according to the charge employed, the sides of the submarine _should_ be compressed sufficiently to cause fatal leaks, while even at a greater distance stability _should_ be destroyed. At the Portsmouth experiment the “dummy” submarine consisted of a barrel sunk some 10 feet below the surface of the water to represent a submerged boat. This was attacked and destroyed by the torpedo-boat destroyer _Starfish_ in the following way. When within striking distance of the barrel, the boom was dropped and the gun-cotton exploded by electrical contact. The officers who carried out the experiment are reported to have said that any submarine within an area of 60 feet of the outrigger boom when the explosion occurred must infallibly have been annihilated by the bursting of the charge, and that if a submarine came up to within a 1,000 yards of a boom-fitted destroyer, it would certainly be done for. [Illustration: EXIT SUBMARINE. ]