In Fig. 13B is shown the diagram of circuits. The letters _d d_ indicate the spheres of the transmitter, which are connected, one to the vertical wire w, the other to earth, and both by wires _c′ c′_, to the terminals of the secondary winding of induction coil, c. In the primary circuit is the key _b_. The coherer _j_ has two metal pole pieces, _j¹ j²_, separated by silver and nickel filings. One end of the tube is connected to earth, the other to the vertical wire _w_, and the coherer itself forms part of a circuit containing the local cell _g_, and a sensitive telegraph relay actuating another circuit, which circuit works a trembler _p_, of which _o_ is the decohering tapper, or hammer. When the electric waves pass from _w_ to _j¹ j²_ the resistance falls, and the current from _g_ actuates the relay _n_, the choking coils _k k′_, lying between the coherer and the relay, compelling the electric waves to traverse the coherer instead of flowing through the relay. The relay _n_ in its turn causes the more powerful battery _r_ to pass a current through the tapper, and also through the electro-magnet of the recording instrument _h_. The alternate cohering by the waves and decohering by the tapper continue uninterruptedly as long as the transmitting key at the distant station is depressed. The armature of the recording instrument, however, because of its inertia, cannot rise and fall in unison with the rapid coherence and decoherence of the receiver, and hence it remains down and makes a stroke upon the tape as long as the sending key is depressed. The principal applications of wireless telegraphy so far have been at sea, where the absence of intervening obstacles gives a free path to the electrical oscillations. The system is also applicable on land, however, and no one can doubt that if the Ministers of the Legations shut up in Pekin had been supplied with a wireless telegraphy outfit, neither the walls of Pekin nor the strongest cordon of its Chinese hordes could have prevented the long sought communication. The full story of mystery and massacre would have been promptly made known, and the civilized world have been spared its anxiety, and earlier and effective measures of relief supplied. As the art of telegraphy grows apace toward the end of the Nineteenth Century, individuality of invention becomes lost in the great maze of modifications, ramifications, and combinations. Inventions become merged into systems, and systems become swallowed up by companies. In the promises of living inventors the wish is too often father to the thought, and the conservative man sees the child of promise rise in great expectation, flourish for a few years, and then subside to quiet rest in the dusty archives of the Patent Office. They all contribute their quota of value, but it is so difficult to single out as pre-eminent any one of those which as yet are on probation, that we must leave to the coming generation the task of making meritorious selection.