"The object of the invention is to increase the probability of hitting at a greater distance by causing the torpedoes launched in the usual way to stop at a predetermined distance from the launching place, in case they have not already been exploded by shock against any object, and to thereupon adjust themselves at a predetermined depth of submersion, in order to act for sometime as mines of the sub-floating or unanchored type and to enable the mine field to be easily formed at any desired distance from the launching place."