Rather more recently, Captain Ericsson's torpedo attracted the attention of the American government. It had one feature of a remarkable character--a hempen cable utilised as a tube or pipe by making the centre hollow. The torpedo, a cylinder of light galvanised iron, was about ten feet long by nineteen inches in diameter, and was charged with nearly four hundred pounds of nitro-glycerine. It was towed by a steamer, with a tubular cable or rope half a mile long. When brought into a desired position, the torpedo was propelled swiftly in any direction by compressed air driven through the tubular rope. The torpedo could be wound in so as to be any less distance than half a mile from the steamer. One rather fails, however, to see how the commander of the steamer is to send the explosive matter against an enemy's ship exactly at the right time and in the right direction. The Whitehead or fish torpedo, one of the kinds now being experimented upon by the English government, appears to be a very elaborate contrivance. It is a sort of submarine rocket, a cigar-shaped iron case five or six yards long by about half a yard in diameter at the thickest part. At one end is a charge of three or four hundred pounds of dynamite or of compressed gun-cotton, with a pistol or trigger-detonator to ignite it; then a pneumatic chamber for compressed air, with an apparatus for maintaining the torpedo at any predetermined depth below the surface of the water; then an air-chamber, tested to a thousand pounds on the square inch, and containing an air-engine with compressed air; and lastly, a double action screw propeller. So much for the torpedo; but how to make it travel along and then explode? It is either driven into the sea out of an apparatus called an ejector, fitted in the bow of a steamer built for the purpose, or it can be launched from a special carriage placed on deck. The arrangements can be so made that the torpedo will travel along at any depth below the water varying from one foot to thirty feet, for a horizontal distance of a thousand yards, and with a speed of seven miles an hour. A torpedo-vessel called the _Lightning_ has just been built by Messrs Thorneycroft and Donaldson for the Admiralty, to contain two or more of these torpedoes, and to eject them one at a time against an enemy's ships. The idea is, to steam to a distance of a few hundred (less than a thousand) yards from the enemy, and eject a torpedo, with its engine, screw, &c. working, in the right direction; the head of the missile, if it dashes under water against an enemy's ship, will explode, and burst a huge hole in the ship's bottom. Or by another adjustment the explosion can be timed to occur in a definite number of minutes after the ejection. A missile of great cost this will be, whether it hits the enemy or not; seeing that the whole of it will be hurled to fragments if it explodes at all; a cost, per missile, of four or five hundred pounds sterling.