THE FIELD OF EXPERIMENTAL RESEARCH. 127 



The ordinary high-frequency apparatus for obtaining discharges of 

 high potential from alternating currents gives onl}" a rapid succession 

 of discharges, each consisting of a few rapidly dampened oscillations. 

 T^hese discharges occupj^ but a small fraction of the total time. This 

 is very different from a continuous sustained wave train, with the suc- 

 cessive waves of equal amplitude following each other without break. 

 Such sustained waves will, doubtless, be of use in research, especially 

 in vacuum-tube work, and they would of course convey much more 

 energ}' than the usual broken or interrupted discharge known as a 

 high-frequency discharge. 



Some six or seven years ago I endeavored, while working- upon the 

 subject of high frequency, to fill the gap. The result was an appara- 

 tus which, with its modifications, deserves more study and experiment 

 than I have been able to give to it. A brief description may not be 

 out of place. A large inductance coil with a heavy iron wire bundle 

 for a core, a coil of relatively few turns with no iron core, and a con- 

 denser of variable capacity were connected in series across the mjlins 

 of a 500-volt electric circuit. The smaller coreless coil and the con- 

 denser were arranged to be shunted by an adjustable spark gap with 

 polished ball terminals. By simply closing for a moment the spark 

 gap so as to form a low-resistance shunt around the condenser and the 

 small coil and afterwards slowly separating the balls, the local circuit 

 of the condenser, small coreless coil, and shunting gap become the seat 

 of sustained oscillations, the frequency of which depends upon the 

 relation of inductance and capacity in the local circuit. The energy 

 supplied is that of a continuous current through the large inductanfe 

 coil with the heavy core. The action of the apparatus is easily com- 

 prehended 1-W a little stud3^ The oscillating current in the local cir- 

 cuit may be made to induce much higher potentials in a secondary 

 circuit inductively related thereto. In this case the turns of the sec- 

 ondary in relation to the primary are, as usual, such as to step-up the 

 potential. In other words, the potential developed in the secondar}" is 

 determined bj^ the transforming ratio. 



We thus have a high-frequency apparatus in which the waves are 

 sustained in an unbroken series, and we employ as the source of energy 

 a continuous current circuit. It shows that we may continuously sup- 

 ply energy to an oscillating system and so keep up the amplitude of 

 electric oscillations, the f requeue}' of which is that due to the capacity 

 and inductance of the part of the circuit in which oscillations are set up. 



While, in the forms of high-frequency apparatus alluded to, we ma}' 

 obtain almost any differences of electric potential up to millions of 

 volts, assuming the apparatus large enough for the work, we do not 

 get a sustained s(^paration of positive and negative charges, as in the 

 static machine, or in a less complete degree with the inductive coil. 

 Professor Trowbridge, of Harvard, has, however, made use of large 



