consists of a brass body having a percussion anvil screwed into its lower end. A spiral spring surrounds this anvil, projecting slightly above it and forming a seat for a light case holding the fulminate, which is of a very sensitive composition. Covering the top of the fuse-case, and just clear of the fulminate-case, is a light copper dome. A slight blow on this dome presses it in and drives the fulminate down on the anvil. _McEvoy’s Improved Percussion Fuse_ consists of a fuse-case containing an ordinary spring gun-lock, nipple, and percussion-cap. The hammer of the lock is held back by a vertical rod free to travel in a guide. On top of the rod is a ball held in place lightly by the upward pressure of a spring. In case that the torpedo is struck and tilted over the ball falls from its seat on the rod, the latter is forced up by the spring, releasing the hammer and exploding the percussion-cap. _Friction-Fuses._ Friction-fuses as a rule consist of some arrangement by which an ordinary friction cannon-primer is exploded. This is done by attaching a firing laniard to the friction-bar of the primer and either leaving it free, so as to fire at the will of the operator, or attaching it in such a way that the momentum of a vessel catching it will pull it. McEvoy’s improvement on Singer’s percussion fuse consists in attaching the laniard of a friction primer to the heavy cover. [Illustration: Barrel Torpedoes with Friction-Fuses.] _Chemical Fuses_ [Illustration: Chemical Fuse.] are those in which substances separated until required for action are then brought into contact and unite chemically with an explosive effect. _Sulphuric-acid Fuse._ This fuse consists of a brass fuse-case containing the magazine and crowned by a thin lead cylinder containing the chemicals, which consist of a small closely sealed glass phial of sulphuric acid placed in the tube and packed with a mixture of potassium chlorate and loaf-sugar. A slight blow on the lead cylinder breaks the bottle, thus permitting a contact between the explosive mixtures. _Harvey’s Torpedo-Fuse._ The principle of this fuse is precisely similar. The bottom of the firing-rod is in this case hollowed and partially packed with the potassic chlorate and loaf-sugar mixture. Over it a small bulb containing a few drops of sulphuric acid is placed and packed carefully with raw cotton. The mouth of the hole is then sealed with a lead capsule. The firing-rod is itself suspended over a firing-pin against which it is driven by the levers on the top of the torpedo. _Electrical Fuses_