Sept. 1930 A N N U A L REPORT OF ELECTRICAL COMMITTEES 751

has continued to show the following advantages: less maintenance, ease of operation, faster manipulation of the screw-down, and simplicity of control. All of these factors are of vital importance and result materi­ally in improved efficiency and increased production of the mills.

The control for reversing mill motors has been improved. This improvement includes the advantages gained on voltage control as applied to screw-downs, and simplified voltage control of reversing mill drive by controlling the fields of individual exciters for the motor and generator fields of a reversing mill drive. This has greatly reduced the maintenance on the field control equipment for reversing mills and has permitted simpler and more sturdy apparatus for field control. I t has practically eliminated the high inductive arc on the field control panel contactors when a mill motor is accelerated and decelerated.

During the past year the installation of photoelectric cells for use as flag switches has incresed. In addition, the successful operation of the photoelectric cell has created other uses, such as direct and recording tem­perature indicators to replace the present pyrometer counters for sheets, tubes, billets and ingots, fire preven­tion, etc. The field for this little device is spread­ing rapidly and the demand for photo-electric cells in the steel mills in the next few years will be greatly in­creased. The design of this apparatus lends itself to practically any application where it is desired to auto­matize a mechanical operation or adjust an operating condition to obtain increased production.

Extended research and experiment are being made in the economical use of fuel in steel mills. The elec­trically operated recording calorimeters and electrically operated gas meters are being used to control the com­bustion automatically and more economically.

The use of electric welding has developed enormously in the steel mills. Particularly of note is the develop­ment in the electric welding of steel tubes.

A new mill which eliminates all hand and mechanical puddling, has been completed at Pittsburg for the manufacture of wrought iron. This plant is electrically equipped throughout and is the most modern mill in the world electrically operated for the manufacture of wrought iron. The method of operation consists essentially of pouring molten iron over molten cinder in a ladle under suitable conditions to form a ball. This ball is then formed by a powerful motor driven press into a bloom which in turn is rolled down in the electrically operated blooming mill to muck bar or billets preparatory to being sent to the skelp mills.

Up to this time the limiting feature in the wrought iron industry has been the economical inability to pro­duce wrought iron on a quantity basis. As a result, the principal use of wrought iron has been confined to the manufacture of pipe. With the development of this new method of making wrought iron on an economical quantity basis there will undoubtedly be markets

opened to it where previously it was unable to compete. The growth of blast furnace production is being

greatly assisted by the automatic operation of skip hoists, the application of stock line recorders, pyrom­eters and other features that tend to give the furnace operators more information regarding their operation.

SHORT-WAVE HIGH-POWER RADIO TUBE

Vacuum tubes have been subjects of research for years. Approximately three years ago scientists in General Electric Research Laboratories succeeded in constructing a radio tube having a wavelength of six meters and a frequency of 50,000,000 cycles per second, capable of radiating 10 to 15 kilowatts of energy. This is fifty times as much power as any short-wave tube previously had been able to produce.

Early experiments with this tube were accompanied with some phenomena startling to a layman. Within the sphere of its influence a cold copper bar would blister the hand that picked it up; an incandescent lamp held in the hand, without wire connections with any electric circuit, would light to full brilliancy; similarly a neon tube, upon being touched by anyone, would emit its bright red glow. Electrical instruments, even in rooms other than the one where the tube was, were disturbed or broken. Persons approaching too close to the tube experienced suddenly a comfortable glow of warmth, but if they continued under the influence, increasing pain in limbs and joints. Blood temperatures rose to 100 degrees Fahrenheit in fifteen minutes.

Radio cooking was demonstrated as a possibility. A wire was suspended over a table at a distance of a few feet from the radiating aerial, which was a copper bar about ten feet long. A sausage in a glass container suspended from the end of the wire was soon cooked. Likewise an egg was "fried" in this container, and an apple spitted on the end of the wire was thoroughly baked in a short time. With suitable changes of utensils cookies were baked and water boiled. There were no flames nor other visible evidences of heat ac­companying the cooking.

The vacuum tube from which this weird power emanated was only two feet long and five inches in diameter. However, auxiliary to it was a large and complex array of electrical equipment costing so much that the tube will have but little practical utility until researchers and developers shall have accomplished numerous simplifications.

Quite different applications of the capabilities of this tube have also been under investigation. For genera­tions heat has been used to alleviate pain and cure some diseases. * * * * As yet the high-power short-wave vacuum tubes are being used for experimental purposes only. To bring them into practical usefulness at rea­sonable cost and discover their many possibilities for service to mankind is now our task.—Willis R. Whit­ney, in Engineering Foundation Research Narrative.