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ber of such projections or spots at once, all being welded simultaneously. Spot welding in its various forms finds a large and rapidly extending application, particularly to sheet steel structures, such as steel car bodies, automobile bodies, metal containers, etc. It has become the general method of uniting stamped metal pieces which subsequently are to be enameled. Formerly, for example, handles were riveted to sauce pans before enameling and the rivets were plainly to be seen under the enamel. By spot electric welding the union is effected without visible change in the metal surfaces and the covering of enamel is in consequence uninterrupted and without projections.

The process is capable of further great extensions in its application to the union of overlapped sheets or plates. Riveted joints, always more or less unsightly and often disadvantageous to construction by taking up room and giving an irregular surface, can often be abolished and the spot weld substituted therefor with benefit. Besides its advantage of leaving a smooth surface, it effects a great saving of time and economizes material. As in the case of electric welding generally, the spot weld gives rise to new modes of construction of metal objects and greatly assists the substitution of pressed steel for castings or forgings. ELIHU THOMSON.

ELECTRIC WIRELESS TELEGRAPH. See DEFOREST WIRELESS TELEGRAPH SYSTEM; MARCONI; TELEGRAPHY; TELEGRAPHY, WIRELESS. ELECTRICAL ALARM, or THERMOSTAT, an instrument arranged to give an alarm or announcement when the temperature in its vicinity reaches a pre-determined degree. (See ELECTRIC SIGNALING, Automatic Fire Alarm Signals). Thermostats are also employed to automatically maintain a given temperature by opening and closing drafts, through the medium of electro-magnetically operated devices. Thermostats are operated on open or closed circuits, as desired. There are electropneumatic and mercurial thermostats which operate by expansion of a gas or mercury, respectively.

ELECTRICAL DIAPASON, a tuning fork the vibration of which is maintained by means of electro-magnetism virtually on the principle of the electric door-bell. (See ELECTRIC SIGNALING). This instrument, provided with a resonator, was employed by Helmholtz in his notable experiments on the composition of sounds.

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ELECTRICAL ENGINEERING. trical engineering is probably the youngest of all the professions, for it has hardly been recognized as a regular profession for more than 15 years past. As a result, the men who have reached prominence in it to-day have attained their positions from widely different courses of preliminary training; many of them are men who started life in other lines of work and afterward turned to electrical pursuits on account of the sudden growth and importance of the business. In consequence of this, all methods of preliminary education are represented

and their relative values can be estimated. The argument runs largely between two classes of men-one represented by the so-called "practical man" and the other by the theoretical electrician; the graduate of the machine shop and the graduate of the university. Both of these types have attained success, but the correct answer to the argument will probably be found in a proper combination of the two types. In the past some of the most successful electrical engineers have belonged distinctly to the class of practical men with little theoretical training, but the conditions have changed. In the early days of the profession, there was little theory or predetermination of results and work was carried on largely by guesswork or by cut and dry approximations. At the present time, however, such a state of development has been reached that exactness of result is essential to success and work based upon exact theory becomes imperative. In a stationary condition of an art a man with practical experience only may become very familiar with all the existing types of apparatus and, knowing their various applications, may qualify, to an extent, as an engineer. But the extraordinarily rapid growth of the electrical arts places electrical engineering apart from all the other engineering branches, for new discoveries and theories make radical changes from year to year in the construction and operation of electrical machinery. The engineer whose education is based only upon practical experience cannot keep up with the progress and change resulting from it, and falls behind; whereas, the man with knowledge of the theory, and a mind trained by the theoretical studies and scientific reasoning, easily grasps the theory of the change and readjusts his mind to the new without difficulty or delay. Many instances can be cited of men who have been prominent as electrical engineers, who have been dropped out of place in the course of the rapid progress which has been made, on account of a lack of theoretical foundation in their knowledge. Those who have retained their positions throughout the growth of the art have done so by persistent study along theoretical lines.

In its present state electrical engineering is the most scientific of all engineering professions. A man must be to a great extent a physicist, a chemist and a mathematician, as well as be familiar with machinery and its design, in order to be a worker in the broadest field. Many of the problems connected with other branches of engineering can be solved by common sense and by one's sense of proportion as guided by experience and by the eye. But most of the problems in electricity are invisible, so to speak, and can be understood only through their expression in the form of symbols. Probably no one will dispute to-day that the preliminary education of an electrical engineer demands a special training in those theoretical branches, mathematics, physics, chemistry and mechanics, sufficient to train his mind into accurate methods of thought and reasoning and to supply him with the actual technical information which he will need in the practice of his profession. But theory alone is not all. The human mind is such that it works with difficulty in pure theory without a series of mental pictures to fix and co-ordinate the ideas, and

the study of theory is likely to make little lasting impression unless the physical meaning of the theory is brought out by constant association with actual apparatus which demonstrates the application of the physical law. The best course of training for an electrical engineer would seem to be a broad course of education in general subjects at the preparatory school before entering college, with practical work, if possible, along lines of simple mechanics, such as carpentry, in order to train the mind into a sense of proportion and the relations of parts, which is the basis of all engineering. Next, a college course with general subjects the first year, and afterward, for the remaining years of the course, those general and theoretical subjects which have a direct bearing upon the practice of the electrical profession, such as mathematics, mechanics, physics, chemistry, theoretical electricity, and magnetism and thermodynamics. This should be supplemented by actual daily practical work with machinery operating by the principles covered by the theory studied and demonstrating all the phenomena incident to the theory. After graduation an apprentice course should be pursued in some large electrical manufacturing establishment where the commercial relations of the knowledge acquired in college can be clearly set forth. Large machines can be operated which are not available at a college and experience in the installation of large plants can be obtained, and experience gained in the designing departments where all kinds of commercial apparatus are laid out.

After a few years of this training specialization may begin along the lines selected for the life work but preferably not before. A man makes a mistake to consider himself a qualified electrical engineer after he has been graduated from college, for he is not one. His mind has been trained into a condition where he can readily absorb the principles of the electrical profession, but that is all, and the subsequent apprentice training is as important as the college course, in order to acquire the broad viewpoint from which to make the correct start in the direction in which a man is best fitted. It perhaps means a smaller income the year after graduation from college, but it means much more at the end of five years. But theory and practice are not the only elements necessary for the successful engineer. There are many qualities required in common with other professions; executive ability, business knowledge, presence of mind and ability to handle men; nerve and resourcefulness in handling machinery in times of emergency, are all necessary to the successful engineer. These elements cannot be acquired in the study of theory and practice alone, and many men who have stood high in their college courses have failed afterward in the practice of their profession because of a lack of these qualities. The study of chemistry becomes more and more important as the profession advances, for the branch of electro-chemistry is rapidly developing and is likely to become one of the largest fields in the application of electrical science. And almost above all comes a training in the English language. No man who cannot express himself clearly and concisely in writing or in conversation can hope to attain a prominent position in

his profession. The education of an electrical engineer, however, must never be considered as completed. The art advances so rapidly that constant study is necessary, even to keep up with the progress of the times. But an electrical engineer should be willing to do more than this. He should study to keep ahead of progress and do his share toward the instruction of others. H. W. BUCK,

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Consulting Electrical Engineer, New York. ELECTRICAL MANUFACTURING INDUSTRY. The conditions as to the electrical manufacturing industries in the United States are fairly well revealed in the statistics of the Bureau of the United States Census for 1914, giving the latest authentic figures available, although these be supplemented by later data in various ways that bring the information up to 1917 and that illustrate the swift and enormous expansion of the various electrical arts and applications. Electrical applications divide themselves into two large groups. One of these comprises the production of apparatus; and the other, many times larger, embraces the utilization of the apparatus chiefly through the agency of what are known as "public utilities," such as telegraphy, telephony, electric lighting and power supply and electric traction. One group of industries manufactures operating materials; the other group manufactures "service." In the United States, as sharply contrasted with Europe, these agencies are in the hands of private capital to an overwhelming degree, and the comparative figures of efficiency, economy and earning power are equally on the side of individual initiative and enterprise.

As to the production of electrical machinery, apparatus and supplies, the data are given herewith for 1914, when the total output for 1121 establishments was placed at a value of $359,412,676, against which may be placed the fact that in 1916, three concerns billed a total sales of not less than $305,000,000. The very lowest estimate for 1917 is $600,000,000 and in view of the enhanced cost of raw material it would not be surprising if it ran in excess of that amount. These figures are revelatory of many new conditions governing the electrical arts, such as the change from steam engines to steam turbines in the generation of electrical energy, the increased use of water power, the invasion of electricity into many new fields of supply, industrial, commercial and domestic; the greater use of the electric motor; the advance of electric heating; the supersession of the arc light by the larger incandescent; the complete conquest of the incandescent lighting field by the tungsten filament lamp; the irresistible intrusion of the electric locomotive, not only into steam railway terminals but into the operation of long stretches of main line, where cheap water power is available for the generation of cur

rent.

It will be noted that dynamos have greatly increased in size, and have fallen off in value, owing to this fact. In the early days of the electric-light and power industry it was customary to employ high speed, single valve automatic steam engines for driving belted generators, as the best regulation of speed could be obtained

with engines of that type, for incandescent lighting. The steam economy of those engines was usually as low as a consumption of 40 pounds of steam per one horse power per hour. The mechanical efficiency was rarely as great as 85 per cent and the electrical efficiency of the generators was rarely 75 per cent. Corliss type engines were used for arc light circuits where the load was uniform and close regulation was not so essential. Their economy rarely exceeded_30 pounds of water per one horse power. For incandescent lighting there was an average consumption of at least 101⁄2 pounds of coal per kilowatt hour and for arc lighting 8 pounds of coal per kilowatt hour. This compares with the present Interborough Rapid Transit 50,000 kilowatt steam turbo generators requiring as little as one and one-half pounds of coal per kilowatt hour; while it is understood that the Connell Creek station of the Detroit Edison Company has an economy even superior to that. There is a 60,000 k. v. a. triple steam turbine under construction for the Interborough system, which will have an actual capacity of 70,000 k. v. a. and is expected to have an economy of 11 pounds of steam per kilowatt hour. The increase in the size and economy of hydro-electric generating units is equally notable. The largest water turbines for electrical service are the three single runner units installed in the plant of the Tallassee Power Company on the Yadkin River, North Carolina, with a guaranteed rating of 31,000 horse power under an effective head of 180 feet, and 27,000 horse power under 165 feet at 154 r. p. m. The turbine runner weighs 20,000 pounds, is a single piece of solid bronze and is probably the largest casting of its kind ever made.

It is to be understood, however, that the manufacture and production of electrical apparatus and material is but a small part of the electrical industry as a whole. The total capitalization is placed as high as $12,000,000,000, the gross sales and earnings are rated at above $2,500,000,000, and the number of persons employed at more than 1,000,000. The accompanying figures were published during 1916 which while based on earlier data can be shown to be in many respects far short of the actuality. A conservative estimate for the total service and output value of electricity in 1917

As to the production of apparatus alone, three concerns reported a total around $300,000,000, and one concern reported at the end of 1917 orders on hand to the value of $240,000,000. The increase is by no means wholly in output but must take into consideration the increase in prices as exhibited in the following table which, while applying principally to electric street railway material, is pertinent in many respects to the electrical field as a whole:

1914-16 PER CENT INCREASE IN PRICE IN
TWO YEARS.

A comparison of

not taken into account.

15,000,000 25,000,000 $12,129,660,000

50.000 6,000

120,000,000