﻿162 Messrs. E. W. B. Gill and J. H. Morrell on Short 



the anode, but placed outside the valve and set at various 

 potentials. The best conditions for these cases are still 

 under investigation. 



2. Barkhausen and Kurz were apparently unable to give 

 any explanation of the way in which the oscillations were 

 sustained, while Whiddington assumed that the emission of 

 ions from the filament was discontinuous and occurred in 

 bursts. The authors, on the other hand, do not think that 

 any special assumptions are necessary, and that the ordinary 

 conditions for the maintenance of oscillations by continuous 

 emission will account for all the facts they have observed, 

 provided that the time taken by the electrons to pass between 

 the electrodes is taken into consideration, as this time is of 

 the same order as the period of the short waves. 



In the present paper only oscillations of the Barkhausen 

 type are considered in detail, but the theory can be extended 

 to cover all the types, and an account of some experiments 

 on the last type (with a diode) will be published later. 



It is worth noting that certain writers give the impression 

 that the seat of the oscillations is in the gas or in the 

 electrons in the valve, and that the Lecher wires connected 

 to the valve serve only to demonstrate their existence *. It 

 appears from our experiments that the wires or conductors 

 attached to the electrodes are a necessary part of the 

 oscillatory system. Even with the Lecher wires removed, 

 there will always be some circuit composed of the connecting 

 wires to the batteries or even the valve leads up from the 

 sockets, which will have natural periods of a suitable order 

 for short wave oscillation. This fact seems to have been 

 overlooked in some recent determinations of ionizing poten- 

 tials, where large emissions from a heated filament were 

 used as a source of electrons. Oscillations will take place 

 even when the valves contain a small amount of gas, but in 

 all the experiments described in this paper gas-free valves 

 were used. 



3. It will probably be most convenient first to describe the 

 experiments in detail, and then to set out the theory and 

 apply it to the observed facts. 



Various valves were used, but mostly the Marconi M.T.5 

 valves, which were very kindly given to us by the Marconi 

 Company. These valves consist of a straight filament FF 

 held in the centre of the valve by springy arms. The ad- 

 vantage of the spring is that when the filament is heated and 



* Whiddington's theory is independent of there being any external 

 tuned circuit. 



