Apr., 1935.] CURRENT TO~ICS. 517

Pump test results showed a maximum efficiency of 86 per cent. with discharge of 41,2oo g.p.m, against 656 ft. head. A maximum water wheel efficiency of 91.6 per cent. was obtained at about 0.9 rated load and 554 ft. head.

R. H. O.

Stationary Commutator D. C. Motor.--In a paper by Dr. E. F. W. ALEXANDERSON AND A. H. MITAGG presented at the A. I. E. E. winter convention there was announced the development of the Thyratron motor which has series direct current characteristics and operates on alternating current. It was made possible by recent advances in electron tube applications. One such motor is now on test. It is rated at 400 hp. 625 r.p.m., and 75 hp. at 350 r.p.m., and is intended for driving an induced draft fan. The motor speed may be controlled down to a standstill. It operates from 2300 v., 3- phase, 6o-cycle power and has a stationary armature and revolving field. The electron tubes perform commutation and grid-controlled rectification, the latter providing continuous power control from standstill to maximum speed.

R. H. O.

A New Source of "Kilocycle Kilowatts."--L. D. MILES, in an article in Electrical Engineering for March I935, explains how electric power at frequencies of I,OOO to IOO,OOO cycles per second is obtained at low cost by means of an electronic tube known as the arc tube. The arc tube consists essentially of two electrodes closely spaced in inert gas under high pressure. A general-purpose circuit consists of a choke coil, a stabilizing resistor, a capacitator and an inductor in series. The tube is connected across the capacitator and the inductor, and the output at any desired voltage may be taken from the secondary of a transformer which constitutes the inductor. In high power applications the stabilizing resistor may take the form of the ohmic resistance of the windings of an electro- magnetic field. The cycle of operation is as follows. When voltage is applied, the capacitator is charged through the resistor, the choke causing a momentary pause in the starting cycle. When the capac- itator is charged to the breakdown voltage between the tube elec- trodes, the tube ionizes, acts as an instantaneous short circuit, and allows the capacitator to discharge th rough the inductor-capacitator- tube circuit. Line current inrush is prevented by the choke. At the instant the capacitator is completely discharged, a high current is flowing in the inductor-capacitator-tube circuit. The inductor continues current flow, which overdischarges the capacitator and drives the tube voltage negative, whereupon the arc extinguishes

518 CURRENT ToeIcs. [J. ~. I.

and the tube is again an open circuit. The capacitator again be- comes charged and the cycle is repeated. The circuit arrangement however depends upon the type of load, the wave shape and the frequency desired.

The arc tube is destined to supply cheaper power for industrial utilization because it is adaptable to varying needs, the equipment can be made economically to supply a few watts or to furnish 50 or more kilowatts and the operating and maintenance costs are low. There are many present uses of high frequency power in industry as well as new applications that have been awaiting the availability of cheaper kilocycle power.

R. H. O.

Hot-Air Balloons Again In Vogue.--( Science Service.) Accord- ing to the German science weekly, Die Umschau, hot-air balloons may soon join gliders as popular sports air-vehicles in that country. A Vienna-born aircraftsman, Rudolf Brunner, has revived the almost extinct hot-air balloon by means of a heating apparatus that can be carried aloft in the basket and continue to pour hot air into the bag in exactly regulated volumes, making for easy control of its lifting power and eliminating the need for ballast.

Herr Brunner's " bootstrap " invention consists of a simple type of burner which is easily prepared by any tinsmith. The fuel is crude oil. A pipe carries the burner up to the bottom opening of the balloon, and the spreading-ring there prevents the fabric from coming within igniting distance of the flame. Valves regulate the flame to any desired height. The cost for fuel per flight-hour is about $2.

C.

Atoms Like Magnetic Eggs.--( Science Service.) Dr. R. BECKER of Berlin has succeeded in showing that the atoms in a metal wire are rearranged under the influence of a magnetic field. In his experiment, a wire with a weight attached to its end was twisted, after which it oscillated for ten seconds before the vibrations ceased. A magnetic field, placed around the wire and parallel to it, so successfully lined up the atoms and overcame the internal friction, that the oscillations did not damp out for more than one hundred seconds. 0

In carrying Dr. Becker's work still further PROFESSOR FRANCIS BITTER of the Massachusetts Institute of Technology assumes that the tiny atoms of a metal are egg-shaped and free to turn so that if the metal is placed under tension the atoms will line up with their long axes pointing in the same direction as the applied force. By