Popular Science Monthly/Volume 24/December 1883/The New Profession
IT is but a few years since the practical student of electrical science was limited to the single branch of telegraphy. His choice lay between becoming a telegraph operator and a manufacturer of telegraph instruments. The telegraph operators form a numerous and intelligent body of men; sharp competition exists among them, and for a long time they had scarcely any chance of improving their position, because until recently no other branch of electrical engineering was open to them. But, during the last dozen years, great progress has been made in various and new applications of electricity. Skilled electrical engineers are few; and any one, who has acquired a practical knowledge of several branches of electricity, will find no difficulty in keeping himself profitably employed.
Until lately, the young electrician's great desire was to qualify himself for submarine telegraphy. The work of testing and localizing faults in cables is of a more scientific and interesting character than work in other departments of telegraph engineering. The manufacture of cables is also a subject for particular study, and a fair knowledge of mechanical engineering may be gained by practice in it. Two of the many different departments of electrical engineering, telephony and electric lighting, are becoming especially important, and yet there is great difficulty in finding competent electricians to accomplish the work.
During a recent sojourn in Europe, I learned that not only young men, but educated women also, were studying electrical engineering, and that large fortunes have been made in it. The enormous extension of the telegraphic system, and the wonderful advances made in electricity, electric lighting, telephony, electrical cables, and railways, and in the transmission of power, offer great advantages to persons seeking profitable employment. Telegraph engineering or electrical engineering is a new profession. More than this, it is one which is not yet over-crowded, and it is, therefore, undoubtedly an occupation which many of our college graduates will adopt.
The ultimate value of the advances which have recently been made in electrical science can not now be estimated. The great electrician, Professor Clerk Maxwell, was asked shortly before his death, by a distinguished scientist, "What is the greatest scientific discovery of the last quarter of a century?" His reply was, "The discovery that the Gramme machine is reversible." The ordinary electrician would have called the telephone, the Faure accumulator, or the Edison electric light, the greatest discovery, but Professor Maxwell's deep and sophic mind perceived that in the fact he named, which to so many of us might seem little more than a curious experiment, lay the principle which, if rightly developed, would make practicable the transmission of power.
If, now, we could call back this great electrical engineer, and ask him what recent discovery came next in importance to this, what would he reply? His answer would be the discovery that "a voltaic battery is reversible." The Gramme machine has given us means of transmitting power of electricity. The later discovery enables us to store up electrical energy as distinguished from electricity.
Electrical engineering, which embraces a knowledge of cables, telegraphy, electric lighting, electrical measurement, transmission of power, storage-batteries, and how to localize faults in cables, land lines, and telephone lines, has thus become a subject of the first practical importance.
A prominent department of the electrical engineer's work is the localizing of faults in ocean-cables, which may be of five different kinds: 1. Where the copper conductor makes a "perfect earth." 2. Where the copper conductor is broken, and yet the insulation remains unbroken. 3. Where an "imperfect earth" is made. 4. Faults arising from a hole in the gutta-percha sheath, making a connection between the conductor and the sea. 5. From the establishment of a connection between the iron sheathing and the copper core, by a nail or wire driven in.
The first kind of fault is easily located, because we know the resistance of the cable when it is in perfect working order. If, for instance, it has 10,000 ohms, Or units of resistance, a fault making a perfect earth midway in the cable would give us 5,000 ohms resistance. Or, we know how many ohms of resistance there are to a mile of cable when it is in perfect working order, and, by the use of delicate instruments and by mathematical calculations, we can easily locate the fault.
The location of the second class of faults, i. e., a complete breakage of the conductor, naturally followed by a total cessation of all communications between the two ends of the cable, may be detected in several ways. The charge which the cable will contain is first measured; and, when the charge per mile is known, the amount actually observed will directly give the location of the faults; and the exactness with which the position of the break can be determined is limited only by the accuracy with which the relative charges can be compared. Suppose, for instance, the discharge from a mile of the cable with a given battery, and reflecting galvanometer, is represented by a deflection of ten divisions, and the discharge from a cable containing a broken copper conductor is one hundred divisions, we know the fault is about ten miles from the shore.
A fault of the fourth kind is located very readily. There is a great fall in the insulation resistance, and a slight fall in the apparent resistance of the copper conductor, between the two stations; but messages can be still transmitted, as a part only of the whole current, inversely proportional to the resistance of the fault, escapes into the ocean. If one office insulates the cable, and the other measures the resistance, the fault acts like a fault that is caused by the fracture of both the copper wire and the gutta-percha, but little of the copper core being exposed.
The fifth kind of fault corresponds almost exactly in behavior to a fault caused by fracture of the copper conductor and gutta-percha, in which a considerable portion of the length of copper wire remains exposed to the water. The resistance will vary still less; and there will be a total absence of the feeble currents which result when the copper and iron of a cable are broken and separated by salt water.
Submarine or ocean telegraphy holds a very prominent place in electrical engineering, and the instruments used in it are interesting. In instructing pupils a very curious apparatus is used. It is the artificial or dummy cable, consisting of a number of "resistance-coils," and condensers so arranged as to reproduce all the phenomena and all the practical difficulties that are presented by a real ocean-cable. With a good instructor, this piece of apparatus is of very great service, inasmuch as all kinds of imperfections can be readily and correctly imitated in any part of the circuit.
Still greater interest, perhaps, attaches to the apparatus for showing the retardation that a current experiences in traversing a long cable. This apparatus consists of a series of "resistance-coils," "rheostats," and condensers, having small receiving instruments at a dozen different points in the circuit, representing as many different offices on the line. The receiving instruments are similar to the mirror portion of Sir William Thomson's mirror galvanometer. In this a ray of light falls upon a very small mirror attached to a small magnet; and this rotates around a vertical axis when acted upon by a current that circulates in a coil of wire. These magnets, with the mirrors attached moving one after the other, indicate the time taken in charging the whole length of the circuit.
I. The Storage of Electricity.—Another principal branch of electrical engineering, promising much in the near future, is the great French discovery of the storage of electrical energy. It is among the most important inventions of the last thirty years. The electrical storage of energy must not be confounded with the storage of electricity. An electrical storage-battery is an apparatus for transforming electricity; in it electrical energy is no longer produced directly, but changes its properties. A given source furnishes a certain volume or quantity of electricity, at a certain pressure or tension. In certain instances, it may be important to increase one of these properties at the expense of another, as in mechanics it is often required to transform speed into force or force into speed by means of fly-wheels or driving-wheels. The apparatus which produces this charge is called the electrical transformer. These machines can be divided into two large classes: 1. As regards tension; and, 2. As regards quantity. The storage-batteries of Thomson, Planté, d'Arsonval, and Varley, belong to the quantity class. All these batteries have a common use. They store electrical energy and give it out transformed. Secondary couples are electrical accumulators, as well as transformers.
II. The Electric Light.—It is clear that this wonderful application of electricity is thus far only in its infancy, and that it must either supplement or supplant gas-lighting in the near future. In it educated persons of either sex may, after a thorough course of training, easily find very remunerative employment in a fast-developing branch of the new profession. With all the older professions overcrowded, an electrical engineer's prospects are, to-day, undoubtedly bright, especially if he has some knowledge of mechanics, though this is not absolutely necessary. Very great impetus has, also, been given to electrical industries by the invention of the telephone, electrical storage-batteries, fire-alarm telegraphs, district telegraphs, and the introduction of the electric light into the domain of our domestic economy. In all these branches there are more places than qualified persons to fill them.
III. Training for the New Profession.—The person who is educated simply as a mechanical engineer, or simply as a telegraph engineer, can not at once make himself useful in the wider range of the new profession which has created itself. The requisites for an electrical engineer are, theoretical and practical knowledge of physics, including mechanics and mathematics. The first questions to be asked a parent, who desires his son to be an electrician, are: "Has your son been studying physics at the ordinary school? Has he ever made any experiments himself, or does he see experiments made by the lecturer?" Let this son commence his technical education at once, for he can learn more of real science in the interval of rest, during his technical education, than he will ever acquire if he devotes himself to books. By a technical college we mean one in which a general education in the application of science to industries is given to all the students, and a special education in the applications of science to individual students.
Electrical engineering has thus a deeper interest for the parents of America than they know. A knowledge of mechanical drawing and designing is essential; and new designs of instruments should be put before the students for use and study, as it is important to cultivate in them the powers of original thought and combination. Next to machine designing and drawing, in the education of an electrical engineer, is a practical knowledge of electricity. And by this I mean far more than an ordinary acquaintance with the effects of glass electrical machines, sealing-wax experiments, etc., etc. The knowledge must be experimental, and it must be quantitative, not merely qualitative. No person ever learned electricity from a book. If one wants to know why a particular dynamo is more efficient than another, he must enter on a course of professional education, like that of studying medicine or reading law. Night after night, in England, many young men come thirty miles to learn how the efficiency of an electric lamp, storage-battery, or a dynamo-machine, is actually measured—how to obtain experimentally the characteristic curves of dynamo-machines of different speeds, calibrating galvanometers, testing magnets, etc.
It would not have been extremely difficult to give lectures on electrical engineering twenty years ago, but the development of the science now is so great that it would be an exceedingly laborious matter to prepare a course on the subject without efficient apparatus. Of the importance of such lectures there can be no doubt, and the time will come when the principles, at least, of electrical engineering will be taught in our schools. The new developments of the science and art can hardly be exaggerated; and while at one time scientific men were of the opinion that the popular mind erred in supposing that electricity would supersede steam as a motive power, engines are now employed to produce power, while electricity affords us the very best means yet discovered of distributing that power.
Electricity does not yet take the place of steam, but it takes the place of cogs, wheels, belting, etc.
A word as to the time necessary to become an electrical engineer. It is claimed by some that six months' study suffices to make a good electrician; but experience teaches us that a year and a half of assiduous work would not be by any means too much.
In conclusion, I may say that this is a profession suitable for women of a scientific, studious, or inventive turn of mind. It is not a profession requiring physical force, but rather keen abilities, good mathematical and scientific training, and the special education of the telegraph engineer.
I can not suggest a brighter prospect for young men, or for intelligent and energetic young women, who wish to learn a profession, than this art, which year by year is steadily assuming more and more importance.