Show pr F K H 15 badt nna patented i electro magnetic sentinel which is d elv aigner to give warning at a repost of the approach of a hostile wa on ship to td a submarine mine or to e belr i blode the mine itself automatically iraa such a device was badly needed tl go usual method employed for coast pr ere lection by means of explosive aln up has been to sink them in the to be protected ordinarily in a narrow narro uy channel and from two for on shore connected by tele telegraph grap h ai led telephone the offic officers rs on duty f folio bcd by means of range duders the amov ir ec ments of any hostile vessel when tl ley instruments indicate that the vessel ro directly over the hidden mine a salti rn Is thrown which sets free an ise current which explodes the mir of this method is as it ad keeping up two two se of instruments and two or more op oy acors moreover abe apparatus c 1 I not always be relied upon it may all out of order just at the moment it led needed it can follow the ing of only one vessel at a time and uld night in fogs or storms it Is of lit re or no use aleut badts device is we tonia tic in its action and gives wai in by night as well as by day it simple gimple and direct in its operation 0 a ok requires but one observatory 4 one L f a of instruments and one atten dai tie he when arrangements are made to of plod the mine automatically the cir can be dispensed with an A n coll coil suitably connected is in cured to the mine or torpedo the ft tho of which to te fired by a powerful elect current switched either automatic the ally or at the observatory when 1 the modem war vessel heavily b by iron or steel armor approaches 1 induction coil there thare will be a if disturbance which is instantly indle ed to the officer on duty at the abse atory he watches the vessel and the arper proper moment closes the fuse and explodes the mine in a an automatic device ILA 1 employed 1 arm of an indicator is deflected ui contact Is made which causes the nl naton siou |