An aluminium arm fitted with a copper rod dipping into mercury is attached to the armature of the second sounder, and the rapid make-andbreak between the copper rod and the mercury (about 600 times per minute) serves to fix the frequency of the sparks. The function of this apparatus, or "buzzer," as it is called, is, during the holding down of the Morse key, to cut up the long-continued contact into a rapid succession of sparks, without any attention on the part of the operator, so that all he has to do is to signal shorts and longs in the usual telegraphic manner. These are translated by the buzzer into the requisite mode of disturbance for sparksignaling, and are transmogrified by the receiver into the dots and dashes of the siphon script. 66 This application of ordinary telegraphic signaling apparatus is due chiefly to the ingenuity of Dr. Muirhead, and how perfectly it works may be seen by a visit to the inventor's experimental range between Elmers End and Aldershot, a distance of thirty-four miles, which, owing to the insulating nature of the Kentish chalk formation is held by the inventors to be equivalent to several times that distance over sea. The system has been tested also over the official range of sixty-two miles between Portland and Portsmouth, and with satisfactory results. As already stated, the inventors are satisfied THE RISK OF CONFUSION. 199 that they can eliminate interference beyond a radius of ten miles. Within that distance the problem is more difficult. For ordinary seagoing work, and for communication between ship and shore, they hold that a simple opentuned system is at present almost necessary, because of the complication that would arise if every ship had to tune both a closed oscillating condenser circuit and its attached aerial specially for each station. While the number of vessels sending wireless signals or messages at one time is small the risk of confusion is not very great. But what will be the condition of things when the wireless equipment of ships becomes general, unless some close system of syntonic signaling be devised, it is not difficult to foresee. Sir Oliver Lodge and his coadjutor, Dr. Muirhead, have for some time been pressingly alive to the imminence of this contingency, and they have in consequence been turning their attention to the working out of a contrivance to meet the need, rather than to the covering of great distances by their "wave" system. They will achieve a great thing if they can adapt their apparatus to this purpose, and so make theirs the premier system as regards safety and effectiveness, if only for short distances. It is some reward for their tireless labors in this direction that the first installation of "wireless " telegraphy adopted by one of the cable companies, that on board the two new repairing ships of the Eastern Extension Telegraph Company, should have been allotted to the LodgeMuirhead "Wireless" Telegraphy Syndicate, after a careful consideration of the different competing systems at present in vogue. It remains to give a brief description of two other systems of aerial telegraphy, the inventors whereof are both Americans. The first is that of Dr. Lee de Forest, of which much has been heard in connection with the Russo-Japanese war, the most interesting part of whose invention centers in the "responder," the device by which he replaces the coherer of other methods. This apparatus, according to the description of the company working the system, depends for its action upon an electrolytic principle. Between two electrodes of soft metal is fixed a paste containing some electrolizable fluid, metallic particles, and some viscous material. Under the action of the local battery, minute conducting particles are torn off from the electrodes and made to bridge the gap. The resistance of the device is therefore ordinarily very small, but under the action of the electric waves electrolysis is set up, and minute hydrogen bubbles are generated at the cathode. This suddenly disrupts the conducting chains and greatly increases the resistance of the responder. The oxygen THE DE FOREST METHOD. 201 appears to combine with the anodic metal, while the hydrogen amalgamates with a depolarizing agent mixed with the paste. The action is thus instant and automatic, and allows the use of a telephone as receiver. As a proof of the sensitiveness of the responder, it is said that it will respond to a inch spark 45 feet away with antennæ only 2 feet in height. The receiving apparatus includes also an adjustable inductance, an adjustable capacity, a potentiometer, a telephone, and a fixed capacity. The adjustable inductance and the adjustable capacity serve for varying the time constant of the oscillating circuit, in order that the circuit. may be put as nearly as possible in tune with the transmitted waves. The object of the potentiometer is to obtain the loudest possible sound in the telephone receiver. As regards the sending apparatus, an ordinary alternating current is used in place of interrupters or coils. A special key is employed for breaking the current, and with it a speed of upward of 48 words per minute is said to have been reached. 66 One of the more salient features of the De Forest method is a reactance regulator," the true function of which is to prevent the formation of an arc across the spark-gap in case the energy of delivery to the circuit becomes excessive. Should a tendency to arc at the gap arise, |