operators soon became a prime requisite of the equipment of the world's shipping. Wireless telegraphy has been developed to great efficiency in all the leading navies, and powerful plants are installed on all warships. The United States, Great Britain, and Germany, most noticeably, have established shore stations, by which they can "talk all around the world" from any ship or station. In operation secrecy is most important. For in the navy practically all important messages are sent in code or cipher under all conditions while in commercial work the tapping of land wires or the stealing of messages while illegal is physically possible for the evil disposed yet has never proved in practice a serious evil. The problem of interference, however, seems to have been fairly solved by the large systems though the activity of amateurs is often a serious disturbance for government and other stations. Despite the progress of wireless telegraphy it has not yet supplanted the submarine cable and the land wire, and in conservative opinion it will be many years before it will do so. In fact, since Marconi's work there has been no diminution in the number or amount of cables laid and the business handled, nor is there prospect of such for years to come. While the cable has answered admirably for telegraphic purposes yet for telephony over considerable distances it has failed entirely so that wireless telephony over oceans starts with a more than favorable outlook. But wireless telegraphy to a large extent has made its own field and here its work has been greatly successful. Thus when Peary's message announcing his discovery of the North Pole came out of the Frozen North, it was by way of the wireless station on the distant Labrador coast that it reached an anxious and interested civilization. It is this same wireless that watches the progress of the fishing fleets at stations where commercial considerations would render impossible the maintenance of a submarine cable. It is the wireless telegraph that maintains communication in the interior of Alaska and between islands in the Pacific and elsewhere where conditions of development do not permit of the more expensive installation of submarine cable or climatic or other conditions render impossible overland lines. At sea its advantages are obvious. Everywhere the ether responds to the impulses of the crackling sparks, and even from the airship we soon may expect wireless messages as the few untrodden regions of our globe are explored. CHAPTER XL ELECTRO-CHEMISTRY AND ELECTRO-METALLURGY.