720 



TORPEDOES. 



they will readily take a polish when cold-rolled 

 in the next operation. The sheets are passed 

 singly through a series of heavy, high-polished 

 cold rolls. After the rolling the sheets become 

 harsh, and to remove this they are again an- 

 nealed in the same way. They are then pickled 

 a second time. The 'sheets are plunged into 

 heated tallow to drive away the water without 

 oxidation of the metal. They are next placed 

 in a bath of molten ferruginous tin, and then in 

 a bath of pure tin. In this they soak twenty 

 minutes, the tinman constantly opening and re- 

 opening the pack with his tongs. The tinman 

 hands them to the washman, who plunges them 

 into the washpot filled with tin. They are next 

 placed upon a flat iron plate, and the washman 

 brushes the two sides, removing the excess of 

 tin between them. To give the sheets a polish, 

 the sheets are dipped, one at a time, in the 

 smaller compartments of the washpot. With- 

 out removing the sheet from the tongs, it is 

 passed between a pair of steel rolls into the 

 patent pot. Passing through these rolls into 

 tin below, it is caught, moved along, and raised 

 by means of a cradle to meet another pair of 

 rolls revolving in the surface of the tin bath. 

 Thus as one sheet is rolled into the bath another 

 is rolled out. The sheets are placed in a rack to 

 cool, after which they are rubbed with sawdust 

 or bran to remove the grease. They are polished 

 with flannel or buckskin, and removed into the 

 sorting room for examination and classification. 

 The tests are durability, strength, and color. 

 Besides the acid process, described above, the 

 palm-oil process is sometimes used. But this 

 is a slower and more expensive method, and on 

 that account preference is generally given to 

 the acid process. 



TORPEDOES. Submarine Mines. The 

 torpedo as a weapon of warfare has made great 

 advance within the past fifteen years, both in its 

 offensive and defensive forms, or. in other words, 

 as movable constructions and as anchored mines. 

 In the latter form they are technically known as 

 "submarine mines," and it is to this division of 

 the subject that we shall now call attention. 

 Anchored mines are used almost exclusively for 

 the defense of harbors, and in the present de- 

 velopment of warfare are rarely utilized for the 

 protection of shipping out of port. The com- 

 plicated construction and apparatus consequent 

 on that electrical connection, now generally used 

 for firing mines, make them impracticable, ex- 

 cept where they can be laid from a fixed station. 

 The older methods of mechanical ignition are 

 now for the most part obsolete. (For history 

 and earlier stages of submarine mining see 

 " American Cyclopaedia," vol. xv, page 802, and 

 " Annual Cyclopsedia," vol. ii, p. 717.) The 

 American school of submarine mining is at 

 Willet's Point, the headquarters of the engi- 

 neer battalion of the army, at the throat of Long 

 Island Sound, about 8 miles from New York. 

 Here thorough instruction in this branch of the 

 military art is given to engineer and other army 

 officers, as also to the enlisted men of the en- 

 gineer corps, and material is stored to meet 

 emergencies. The principles underlying the 

 American system are of course the same as those 

 adopted by the military engineers of the more 

 advanced European nations, but in some im- 



portant minor applications of these principles 

 there are features peculiar to our service. 



There are also certain secrets involved in the 

 details of the working and employment of the 

 American torpedo system which are not made 

 known. These are the constructions of the " cir- 

 cuit closer " and of the " firing box," and the 

 plots of the torpedo fields designed for the vari- 



A BUOYANT TORPEDO. 



ous harbors of the country. In the latter case 

 the secret is kept within the penetralia of the 

 War Department, a thing not even intrusted to 

 engineer officers until the actual need of laying 

 torpedoes arrives. But these may be illustrated 

 without trenching on the actual facts. 



Submarine mines may be divided into two 

 general classes electro-contact and self-acting 

 mines. The latter have within themselves the 

 means of ignition in the shape of a small battery 

 of a few cells, and are equally dangerous to 

 friendly and hostile ships. They are only used 

 at times of great urgency or in less important 

 channels to supplement the others. Their sim- 

 plicity of structure and freedom from compli- 

 cated shore attachment make it possible to lay 

 them with great rapidity. But they are liable 

 to become rapidly ineffective as, once down, they 

 can not be tested. For this reason, and the no less 

 potent ones that they threaten all ships alike and 

 can only be safely removed by exploding them, 

 self-acting mines promise to become obsolete as 

 the art of submarine warfare progresses. Elec- 

 tro-contact torpedoes are discharged by the shore 

 circuit, and involve complicated electrical appa- 

 ratus and the highest skill and judgment in their 

 practical use. As compensation for this they can 



