The greatest skill and care is necessary in attempting to clear a channel of mines and torpedoes. Light-draught boats, launches, gun-boats, drag-nets, grapnels, and materials for handling torpedoes at a distance of thirty or forty feet are indispensable. Torpedoes of the Brooks class may be dragged over many times and escape notice. The frame-torpedo requires the aid of counter-mines or large torpedoes extemporized and sunk on them to blow them to pieces. The shallow water both sides of the channel must be carefully and thoroughly dragged for leading wires. Boats on search must proceed with frames rigged from their bows to catch and explode torpedoes in advance. Deep-draught frames of timber must be dragged up or floated down a channel. Muddy bottoms must be thoroughly sounded, and after the search is complete deep-draught vessels cannot pass through suspected channels without torpedo-catchers rigged from their bows. Too close an examination of a torpedo after it is picked up must be avoided. It may almost invariably be easily and safely exploded, and no better disposition can be made of it. EXAMPLES OF THE USE OF TORPEDOES DURING THE PAST TWENTY YEARS. _Whitehead._ Sent from the British frigate Shah against the Peruvian iron-clad Huascar, May 29th, 1877. During the running fight between these vessels, the Shah discharged a Whitehead from a bow tube under water, which failed to reach the Huascar, the reason given being that at the moment of firing the latter changed her course. It is to be presumed that the torpedo in this case was carefully aimed, as there was no cause for great hurry. The Huascar could not be aware of the moment of firing, and the failure appears to demonstrate the great difficulty of using this type of torpedo between rapidly moving vessels at distances of eight hundred yards or over. Sent from Russian steam-launches against Turkish iron-clads off Batoum, December 28th, 1877. The Turkish vessels in this instance were lying at anchor, surrounded by booms of logs and vertical timbers, and having guard-boats out. The Russian launches succeeded in passing the guard-boats and approaching to within less than a hundred yards of the Turks before they were discovered. Two Whiteheads were then launched at one iron-clad, missing their mark completely, both being found on the beach, unexploded, next morning. The attributed causes of the failure were non-familiarity with the complications of the torpedo itself, darkness, and a slight swell. Sent from Russian torpedo-launches against a Turkish revenue vessel, January 26th, 1878. In this instance the torpedo-launches were entering Batoum harbor with the intention of attacking the iron-clad fleet, when they were met by a revenue steamer coming out. Whiteheads were discharged at a distance of less than one hundred yards, and the steamer was struck and sunk. The Lay torpedo has never been used in war.