A note in Nature describes an ingenious arrangement for controlling the direction of torpedoes by means of ether waves. Two solenoids, into which are drawn iron cores, are attached to the rudder head, the core which is drawn in depending, of course, upon the direction of the received current. Two rods projecting above the surface of the water receive the waves and are in circuit with a coherer of special type, which affects a relay in the usual way. The actual processes involved in steering and controlling a torpedo are somewhat as follows: The torpedo, containing a suitable combination of the apparatus above mentioned, is launched from a vessel containing the necessary sending apparatus. Suppose the torpedo goes off its course. Then, by means of a switch, an induction coil is supplied with an electric current, and waves or oscillations are generated. These, on reaching the torpedo, pass into the projecting wire and thence reach the coherer. This operates the relay, closing the secondary circuit. An electric current now flows through a “selector” to one of the solenoids, the iron core is sucked into right or left, and the helm is thus turned. When the torpedo has attained a proper course the switch is opened and the waves cease. The vibration in the neighborhood of the coherer restores it to the original resistance; the current passing through it becomes weaker and ceases to affect the relay coil, which therefore opens the secondary circuit and allows the helm to fly back to the midship position. A large model of the apparatus has been constructed, and it is said to work with entire success under all kinds of conditions. The inventors are Mr. Walter Jameson and Mr. John Trotter. It is stated that Nikola Tesla has American patents for a somewhat similar device. * * * * * In the absence of the author, Professor Dewar’s paper on the solidification of hydrogen was read in the British Association by Sir William Crook. It shows that solid hydrogen presents the appearance of frozen water, and not, as had been anticipated by many, of frozen mercury; hence it is now definitely decided that it is not metallic. The temperature of the solid is 16° absolute at thirty-five millimetres pressure, and it melts at 16° or 17° absolute, the practical limit of the temperature obtainable by its evaporation being 14° or 15° absolute. Thus the last of the old gas has been solidified. It was further mentioned, in connection with these statements, that Professor Dewar had succeeded in liquefying helium. * * * * *