. Review of reviews and world's work. equentand careful adjustment. Hence, it was evident toall concerned in the advancement of wirelesstelegraphy that the production was desirable ofa detector more sensitive and more reliable thanthe filings coherer, and one which upon the cessa-tion of the oscillations in its circuit would atonce automatically resume its normal number of detectors capable of fulfilling theserequirements have been devised in the past fiveyears, among them the Solari mercury auto-coherer, used by the Italian navy ; the Marconiand other magnetic detectors ; the De F
. Review of reviews and world's work. equentand careful adjustment. Hence, it was evident toall concerned in the advancement of wirelesstelegraphy that the production was desirable ofa detector more sensitive and more reliable thanthe filings coherer, and one which upon the cessa-tion of the oscillations in its circuit would atonce automatically resume its normal number of detectors capable of fulfilling theserequirements have been devised in the past fiveyears, among them the Solari mercury auto-coherer, used by the Italian navy ; the Marconiand other magnetic detectors ; the De Forestelectrolytic detector ; the Fessenden heat de-tector, and the Lodge-Muirhead oil-film of these electric-wave detectors, or, morecorrectly, electric - oscillation detectors, whilediffering more or less in principle, effect thesame final result,—that is, they either produceor vary a current in a local circuit in which isplaced a telegraph relay or a telephone they vary the resistance of that circuit and. FIG. 2. (Wireless receiving apparatus. -A, vertical wire; n, /., fil-ings coherer; /.tapper; />, relay ; b, b, batteries; E, ink recorder.) IV/RELESS TELEGRAPHY TO-DAY. 193 thus cause the relay or telephone to respond tothe received signals. At the present time, almost every civilized na-tion has developed one or more systems of wire-less telegraphy. In the United States there arethe De Forest and Fessenden systems ; in GreatBritain, the Marconi and Lodge-Muirhead sys-tems ; in Germany, the Slaby-Arco and theBraun systems, which are now consolidated underthe name of the Siemens-Halske wireless system ;in France, the Ducretel and other , naturally, also claims the Marconi wirelessmethod. In Russia, the Popoff system is used ;while in Japan a wireless system has been de-veloped the inventor or inventors of which arenot definitely known.* IN ALMOST UNIVERSAL USE. It is difficult to ascertain the actual degree ofperfection to which sev
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