For 939 companies in 1907 and for 797 companies in 1902. Number employed 16 Sept. 1912. Figures not available. 1912, 31.91 miles; 1907, 27.52 miles; and 1902, 4.20 miles. Represents 899 companies in 1912, 734 companies in 1907 and 390 companies in 1902. Exclusive of companies doing freight traffic only and in 1902 of four companies not reporting revenue passengers. Exclusive of six companies in 1907 and of 18 companies in 1902, which failed to furnish this information. Exclusive of 12 companies in 1902, which failed to furnish this information. Telephony and Telegraphy.- The general statistics of the telegraph and telephone industries of the country are shown both comprehensively and comparatively in the following table. These two branches of the great modern art of the communication of intelligence are separate and distinct, yet are very closely interwoven in their physical relationships; and at various times and in various ways have been largely conducted financially as one business. The economic reasons for such a combination are not far to seek and are recognized in the existence in most countries of a united telegraph and telephone governmental administration; whereas in the United States such a policy, under the prevailing private ownership, has been declared illegal. American telephone and telegraph systems as to apparatus used and results obtained are in general infinitely superior to anything prevailing elsewhere. A point to be noted in 28,447,265 17,359,605 12.4 -31.4 63.9 28,030,542 17,157,061 12.7 -31.0 63.4 416,723 202,544 -14.6 -58.5 105.7 the accompanying table is the relatively disproportionate magnitude of the younger art, telephony, in all respects, particularly investment and earnings. depots, being placed at 30,000. The annual report of the Western Union Telegraph Company for 1917 is a sufficient indication of revived prosperity now and in recent years. The report TELEPHONE AND TELEGRAPH SYSTEMS - COMPARATIVE SUMMARY: 1912, 1907 AND 1902. 1 Includes farmer or rural lines, and in 1907 and 1912 systems reporting annual incomes of less than $5,000; therefore, except for number of systems or lines and miles of wire, figures do not agree with those shown in other tables. 2 Does not include wireless telegraph systems. Exclusive of 314,329 miles of wire owned and operated by railway companies. Number employed 16 Sept. 1912. The extent to which the condition of the times affect electrical utilities is strikingly shown in the fact that while for the period of eight months in 1917 the American (Bell) Telephone and Telegraph Company's earnings rose from $171,608,490 to not less than $194,337,712, the operating net income was but $47,439,392 as compared with $47,586,666. The whole gain of nearly $23,000,000 was thus negatived with $150,000 more thrown in; but the gain was there all the same, and in due time the larger interest charges due to rapid increases of capital will work out to advantage. On the basis of total operating revenues of the Bell system of $270,000,000 the year 1917 will show at 10 per cent increase an amount well in excess of $290,000,000. For telephony as a whole, including the independent systems, a total of, say, $425,000,000 might be set down. The physical statistics of the Bell telephone system and its growth are strikingly shown in the accompanying table. Telegraphy. As an industry the telegraph showed a remarkable recovery following the outbreak of the European War, and at the end of 1917 there were no fewer than 60,000 telegraph operators engaged at telegraph centres, local offices, brokers' offices, etc., the number of distinctively telegraph offices, including railroad the European War has been felt generally in the export of American manufactures, but in this respect electrical goods have been a conspicuous item. The foreign demand for American electrical apparatus and supplies, even under the severe limitations imposed by lack of ships and many closed markets, has carried the strictly electrical exports from $19,771,757 in the year ending 30 June 1915 to no less an amount than $52,158,773 in the corresponding period 1916-17. The chief gains were in insulated wires and cables from $1,911,850 to $7,191,684; electrical in use in modern power stations on land, connected to two independent induction motors mounted on each of the four propeller shafts. It is quite probable that details as to any part of this tremendous innovation in naval equipment should not be expected until the war is over. Many advantages for this method of propulsion are claimed by the designers and disputed by critics. Three battleships requiring 33,000 horse power each, of the same type, have also been provided for in naval plans; and one of these, the superdreadnought California, cor BELL TELEPHONE SYSTEM IN THE UNITED STATES. batteries from $967,146 to $3,286,674; electric motors from $2,818,743 to $5,895,696; transformers from $624,483 to $1,265,459; telegraph instruments from $76,271 to $539,389; incandescent lamps from $575,072 to $2,301,407; electric meters from $2,818,743 to $5,895,696. Electrical Ships.- A decided novelty in the field of electrical manufacture is the equipment of electrically propelled ships. The world is familiar with the use of launches driven by storage batteries and with submarine boats in which the same motive power is employed; but in the modern electrical ship propulsion is secured by means of electrical energy fed from steam turbine generators to electric motors mounted on the propeller shafts. The success of this method in the United States collier Jupiter would seem to be very emphatically evidenced in the provision in the Navy Bill of 1916 for four great battleships or cruisers each requiring 180,000 horse power delivered to four screw shafts turning at full speed at about 250 revolutions per minute, which yield a rate of travel through the water of 35 knots per hour. Each of the ships is to have installed four high speed turbine-driven generating units, similar to those responding to the present direct steam-driven Arizona, is under construction. No other nation has yet ventured on such an experiment. THOMAS C. MARTIN, Secretary National Electric Light Association. ELECTRICAL MEASURING INSTRUMENTS. The four fundamental electrical quantities which are being constantly measured in electric circuits are ohms, amperes, volts and watts. Another quantity of much commercial importance is watt hours. The usual method of measuring ohms, that is, the electrical resistance of a circuit, is to use a Wheatstone Bridge, which is described elsewhere. The electrical resistance of a circuit may also be measured by what is called "fall of potential method," which consists in sending a measured current through the circuit and measuring the difference of potential between the terminals of the circuit, as illustrated in Fig. 1. When the current is measured in amperes and the difference of potential is measured in volts, the resistance is obtained by taking the ratio of the volts to the amperes. The instruments used in this measurement are |