=To Fire.=—Make connections with the firing-battery, or with the A machine (_Plate IX_). When using the battery, close the hand-firing key at the moment it is desired to fire. When using the A machine, press the key F of the firing-key, and keep it down; turn the crank of the machine rapidly, and at the instant it is desired to fire, press firmly the key T of the firing-key (the key F being already down). The Service Torpedo must be immersed 10 feet, and from ships may be safely exploded at 35 feet from the side. =To Test the Circuit from Boats.=—The spar leading-wires are brought directly to the machine, (_See Plate XVI_), _but not connected until the torpedo is submerged_, when the circuit may be tested by connecting it to the binding-screws of the C machine, turning the crank of the machine and pressing the key T, as for testing the detonator. Or, the testing-magneto may be used to test the circuit. _The firing-battery must not be used to test the circuit._ =To Fire.=—Make connection with the battery (_Plate XV_), or with the C machine (_Plate XVI_.) When using the battery, close the hand-firing key at the desired instant. When using the C machine, manipulate the keys as directed for the firing-key of the A machine. The Service Torpedo must be immersed not less than 10 feet, and may be safely exploded at a horizontal distance of 22 feet from the boat. EXERCISE TORPEDO. =Pattern D.—Plate II.= =Priming the Exercise Torpedo.=—Remove the transportation thumb-screw and loosen the thumb-screw on the lug of the hinge. Throw back the cover, replace the second wet block of gun-cotton from the top with a dry 2-inch block, or four ½inch blocks, and put the cover back in place; insert the spindle, to be found in box 53, through the loops on one side and screw down taut against its shoulder; screw down also the thumb-screw on the lug of the hinge. _It is absolutely necessary that this case be closed water-tight._ The wet gun-cotton removed is to be placed in one of the empty exercise torpedo-cases, to be dried when opportunity offers. =_Note._=—Do not allow the dry primer to remain in the exercise torpedo any considerable length of time before use, as it may absorb enough moisture to prevent detonation. The detonator is tested and spliced, and the torpedo fuzed in the same manner as directed for the Service Torpedo. =Shipping the Exercise Torpedo.=—To be done in the same manner as prescribed for the Service Torpedo. The Exercise Torpedo may be used from either a boat‘s or ship‘s spar. It may be safely exploded at an immersion of 5 feet, and a horizontal distance of 20 feet. PREPARATION OF THE CONTACT TORPEDO. =Pattern D.—Plate V.= =To Convert a Service Torpedo into a Contact Torpedo.=—Attach a circuit-closer, Pattern B, to the frame on the lower head of the torpedo by screws through the lugs.