Judsonia weekly advance., 1915-02-03

 be said of the harbors of Germany.
 But these eontrivanees for harbor defense, while much formidable and dangerous to an enemy, are harmless to friendly ships. They what are known observation mines," and, being nected by wire with the shore, set off by the sending of an electric spark at a moment when hostile vessel may happen to be within range of their tremendous explosive activities
 All the navigable channels of the harbor of Portsmouth for example. at this moment guarded by an elaborate system of mine fields" which protected by rapd-fre guns shore. At night they are under constant watch, as we'll as by day, being swept by huge searchghts.
 Such mines are hollow spheres of galvanized iron three feet in diameter, each containing 500 pounds of guncotton, which is lighter than water, so that they float. They are anchored few feet below the surface in series of lines across a channel about eighty feet apart in each line. If enemy's ship were to succeed by good luck in getting through line without being blown up, she could hardly pass another
 The area of water surface covered by a mine field is laid off (by careful survey) in checker board of imaginary squares This checkerboard is reproduced small scale table in derground casemate on shore, which is part of fort. Suppose hostile vessel to approach Two telescopes are aimed at her from points on shore hundreds of yards apart, their lines of sight crossing, of course, at the spot where she floats The telescopes are electrically connected with two pointers that move the table. Moving with the telescopes, the ends of the pointers meet on the square corresponding to the one where lover the mine feld) the vessel actually is. button mark ed with the number of that square is touched, and tbang!-she is blown sky-h1gh. &--------
 Small steaaEagefs especially equipped for the pur -p6se are used in the business of planting these mines, and the work being of such great import ance, the men who undertake it are highly trained. Theirs is branch of the coast artillery which does it's fighting literally under water, and apart frop fho rnpc chani ilc oftb they must have fairly expert acquaintance with electricity and the chemistry of explosives.
 A part of the preliminary work of establishing mine field consists in making soundings. The depths all the surveyed area having been ascertained wire ropes are measured off into responding lengths, heavy leaden sinker tor anchor) being attached to one end of each, and mine to the other end. By this simple means the sphere of galvanized iron is made to float just many feet below the surface as may be desired. Recently, however, ingenious automatic chor" has been contrived, by which, no matter what the depth, exactly the required submergences for each submarine may be obtained offhand.
 AS yet experience in actual warfare has not afforded practical demonstration of the usefulness of such observation mines. But of their destruc- tive power there can be question Many ex- perinients have been made with them in the blow ing up of old hulks. and this side of the water not long ago, miniature ship of war was scat tered in smfthereens at Fort Totten. N r., by mine of corresponding size ignited by an electric spark from distance of mile and quarter
 From such trials the conclusion ber he@-a7ssas that fha Ss-i,-s = =atssaF