274 PROCEEDINGS OF THE AMERICAN ACADEMY. 



length of the gap the discharge begins to hiss and become unsteady. 

 For other values of the main current, Ig, the curve would be slightly 

 different, but, in general, the best results are obtained with a gap 

 length of from ,04 to .09 mm. 



The effect of changing the pressure of the hydrogen was investigated. 

 Apparently atmospheric pressure gives the most satisfactory results, 

 although, for decreased pressure, the oscillations are possibly slightly 

 more intense until the pressure of about 10 or 20 cm. is reached, when 

 they rapidly become weaker. Increased pressure is decidedly det- 

 rimental. 



Before entering upon an explanation of the curves and results it is 

 essential that a comprehensive idea of the operation of the system be 

 had. To this end the following brief review of the events during one 

 cycle is introduced, the details of which will be considered more at 

 length later. It is clearest, in tracing the sequence of phenomena, to 

 begin at the instant after the system has been started, when the poten- 

 tial of the primary condenser Ci (Figure 3) has attained a value suffi- 

 cient to break down the high resistance of the gap. The gap resistance 

 rapidly falls to a very low value as the discharge of condenser (\ and 

 the main current lot which was previously flowing into Ci and which 

 remains practically constant on account of the inductances Lq A> rush 

 across the gap and through the primary coil Xi. This current rush 

 takes place according to a definite positive loop of current with respect 

 to time, the shape, amplitude, and duration of which depend upon the 

 constants of the circuit, the rapidity of absorption of energy by the 

 secondary circuit, and, to a slight extent, upon the conditions of 

 the gap and strength of the main current Ig. The condenser Ci is 

 discharged and charged somewhat in the opposite direction by this 

 positive current rush. If conditions are right the discharge stops as 

 soon as /i becomes zero, there being no inverse current. The secondary 

 receives a certain increment of energy from this discharge, and con- 

 tinues to oscillate after the primary discharge stops. 



This absence of inverse current above referred to is due to the com- 

 bination of three conditions. First, and most important, is the practi- 

 cally instantaneous re-establishment of the high initial gap resistance 

 when the current becomes zero, due probably to the formation of an 

 insulating oxide film on the aluminum ; second, the higher cathode 

 drop of the anode metal ; third, the absorption of energy by the sec- 

 ondary, although rectification usually takes place without this aid. 



At the end of the above mentioned current-rush the current through 

 the gap is zero and the condenser Ci has an inverse charge. Since the 

 main current must remain constant it is now flowing into Ci, it having 



