means of obtaining Continuous Electrical Oscillations. 261 



In the next place, the magnetic field required careful ad- 

 justment. If it is too strong, the arc cannot be maintained 

 without constant interruption. If too weak, the oscillations 

 are feeble. 



The various factors— gas,, field, arc-length, rotation of 

 carbon and water cooling — all require exact adjustment to 

 obtain the best result. In laboratory or in lecture expe- 

 riments, when effects are only required for a few minutes, 

 this is not difficult; but if the apparatus is used as a trans- 

 mitter in wireless telegraphy, it must be possible to maintain 

 constant for hours together the production of the oscil- 

 lations, and so far I have not found that this is a very easy 

 thing to do. I have tried many methods for making the 

 arc self-regulating as to length, bat without success. The 

 best plan is hand regulation by a skilled assistant. There is 

 a particular length of arc which for given current and 

 voltage produces the oscillations most effectively, and this 

 length has to be maintained constant. 



When employed as a wireless telegraph transmitter, the 

 question which presents itself for consideration is the efficiency 

 of the arrangement as an energy transformer. We supply 

 the arc with continuous current power, and we create by it 

 high-frequency persistent oscillations in the antenna. There 

 are several sources of energy dissipation. In the first place, 

 the arc must be arranged in series with certain regulating or 

 ballast resistance to permit of adjustment. I have found 

 that very good effects are obtained when working off a 

 400-volt public supply of direct current or from a 500-volt 

 continuous current 5 k.w. dynamo. Then from 50 to 1U0 

 volts may be dropped in the regulating resistance when 

 working with an arc of 8-10 amperes. 



In the next place, there is a large production of heat in the 

 chamber containing the arc, the greater part of which is 

 removed by the cooling water. We have then a portion of 

 the power converted into high-frequency current in the con- 

 denser circuit, and this dissipates itself partly as heat in the 

 inductance and condenser, and only a fraction of this power 

 is radiated by the antenna. We are not really concerned to 

 know the manner in which these heat losses are distributed. 

 We cannot subject the matter to mathematical discussion 

 unless we make certain assumptions as to the form of the 

 curve representing the oscillations, which form has not yet 

 been determined. I have found by experiment that the power 

 factor of the arc when working is not far from unity, and 

 hence the power given to the arc in the form of continuous 

 current can be very approximately determined by the product 



