124 Commendatore G. Marconi [March 13, 



placed two other discs C^, Cg, which may be called polar discs, and 

 which also can be rotated at a high rate of speed. 



These polar discs should have their peripheries very close to the 

 surface or edges of the middle disc. 



If a small amount of energy is used, stationary knobs or points 

 may be used in place of the side discs. 



The two polar discs are connected respectively through suitable 

 brushes to the outer ends or terminals of two condensers K, joined in 

 series, and these condensers are also connected through suitable 

 inductive resistances to the terminals of a generator, which should be 

 a high-tension continuous-current dynamo. 



On tlie high speed or middle disc a suitable brush or rubbing 

 contact is provided, and connected between this contact and the 

 middle point of the two condensers is inserted an oscillating circuit 

 consisting of a condenser E in series with the inductance, which last 

 is connected inductively or conductively to the aerial. 



If the necessary conditions are fullilled, and a sufficient E.M.F. 

 is employed, a discharge will pass between the outer discs and the 

 middle disc, which discharge is neither an oscillatory spark nor an 

 ordinary arc, and powerful oscillations will be created in the signalling 

 condenser E and oscillatory circuit F. 



I have found that in order to obtain good effects a peripheral 

 speed of over 100 metres per second is desirable ; therefore particular 

 precautions have to be taken in the construction of the discs. Elec- 

 trical oscillations of a frequency as high as 200,000 per second can 

 be obtained. 



The apparatus which I have had so far constructed is on a large 

 scale, and unsuitable for demonstrations in a lecture hall. I hope, 

 however, very soon to be able to show before some scientific society 

 the effects produced. 



The apparatus works probably in the following manner : — 



Let us imagine that the source of electricity is gradually charging 

 the double condenser and increasing the potential at the discs, say Cj 

 positively and Co negatively ; at a certain instant the potential will 

 cause the charge to jump across one of the gaps, say between Co and 

 A. This will charge the condenser E, which will then commence to 

 oscillate, and the charge in swinging back will jump from A to C^, 

 which is chvarged to the opposite potential. The charge of E will 

 again reverse, picking up energy at each reversal from the con- 

 densers K. The same process will go on indefinitely, the losses which 

 occur in the oscillating circuit E F being made good by the energy 

 supplied from the generator H. 



If the disc is not rotated, or rotated slowly, an ordinary arc is at 

 once established across the small gaps, and no oscillations take place. 



The efficient cooling of the discharge by the rapidly-revolving 

 disc seems to be one of the conditions necessary for the production 

 of the phenomena. 



