The San Francisco call., 1898-03-31
CRUISERS, MINES AND TORPED0ES
Some Interesting Information on Subjects That DeeDlu Concern the Public, but Are NOf Gen.
 efdllu Understood.
BY WILLIAM C. BoYhES.

The loss of the Maine and the
 strained relations with Spain (for other
 reasonS) seem to have awakened 8 | lively general interest in torpedoes and
 vessels of war. People generally know little of either, and as a reply to a
 single letter this column is published, 1 but the information given will doubt
 less satisfy most of those who wish
 enlightenment on these subjects. In
 what follows technical terms are alto-
 gether avoided as far as at all possible,
 the object being to instruct the general
 reader-not the expert. The letter to
 which this may be called a reply fol- lows:
 | The Manager Call-Sir: As I know nothing of torpedoes, the use of a torpedo catcher, how a torpedo is elected, what
 a cruiser is as distinguished from fight
 ing ship, or much else about such mat | ters shall esteem it favor etc.
 To begin with, it is necessary to know what a torpedo Is. The term used to be applied to any submarine agent that had destructive power, but to-day | a torpedo is exclusively something pro-
 pelled at an object for its destruction. Submarine defense is divided into four distinct classes, viz: CD Ground
 mines. @ Buoyant self-acting mines. (3) Controlled buoyant mines, and (Q torpedoes.
 Q) A ground mine is constructed by placing a suitable amount of explosives of high power-properly protected-ln position at the bottom of a harbor or river. They are usually somewhat sunk in the sand or mud, but rarely in hard rock. Their principal advantages are that they permit the use of heavy charges of explosives without the cor responding difficulty of mooring. and that their position Is easily determined and can always be relied on. The num- Der of these mines which it is possible to place Is limited, for they can only be used In shallow water. They are in- variably electrically connected with a shore station from which they are fired at will.
 2. The buoyant, self-acting mines may be fired either by simple mechan- ism or by an electrical device. They usually consist of a metal case shaped much like an inflated balloon which is partially filled with dynamite or gun cotton. On the top of the case there protrude half dozen or so small tubes of foot or more in length, and a ship passing and striking either of these lit tie tubes violently would break a glass inner tube which by simple chemical action in the purely mechanical class releases a heavy weight which, falling on the explosive in the bottom of the case, acts as a detonator and fires the mine. The electrical automatic mine Is constructed in much the same way, but the explosion Is caused by the breaking of an electrical current when either of the tubes at the top of the case come into violent contact with an- other body Of course, this class of mine depends entirely for its usefulness on the enemy's ship striking one of the firing tubes.
 3. The term controlled buoyant mines Is applied to those which can be fired only by electricity from the shore. They do not differ much from the automatic mines, and a combination of both has proved successful. These controlled mines are usually laid in groups, and whenever possible and practicable the electrical connections are made so that one or any number may be fired at once. The detonation is of course a very simple matter. This form of sub- marine defense, though, Is extremely expensive, which prevents its more ex- tended use. These mines, as we'll as the automatic, are moored by chain or wire cable to a heavy anchor, and by an ingenious device 1t is possible to keep them at any depth below the sur face which may be deemed advisable. Here it is interesting to note that it is unsafe to moor one mine nearer to an- other than at least six times the radius of it's striking distance That is to say, if a mine would work destruction a hundred feet from where it Is anchored there must be at least 500 feet between it and its next door neighbor, and 800 feet would be better.
 4. For lack of space only one variety of torpedo-the automobile-can be de- scribed. But it Is practically the only torpedo now in use. These little en- zines of war are really small vessels in themselves. Shaped much like cigar. they have a couple of propelIers, rud- ders and half a dozen watertight com partments. The nose or percussion end holds the cap, then comes the compart- ment devoted to explosives. There is an air reservoir, @ balance chamber (where the mechanism for keeping the machine on an even keel is); there is the engine compartment and the buoy ancy chamber. The delicacy and accu- racy of the mechanism of these instru- ments of destruction are amazing. Not only can they be aimed and fired with almost the accuracy of a gun. but they can be made to stop and come to the surface at any desired distance from the ship firing them, and recent experi- ments tend to show that it will be pos sible in the near future to even Zig-zag their course with accuracy. A torpedo is elected by placing it In tube some thing like large grooved pipe. The amount If energy required to launch it is very small, and the moment it touches the water its engines (worked usually by compressed air. but some times electrically) start automatically. The speed can be regulated in any de-