144 



NA TURE 



[December 2, 1909 



much reduced. It is. however, possible, as I have shown, 

 to duphcate the receiving circuits so as to capture the 

 energy of both the waves even with close coupling of the 

 transmitter transformer ' (Fig. lo). 



A method of creating feebly damped oscillations has, on 

 the other hand, recently been developed, generally known 

 in Germany as Wien's method, or the method of quenched 

 sparks, which is based on the fact that if we can quench 

 or stop the spark in the condenser circuit after the first 

 few oscillations, the oscillations of the antenna then take 

 place freely and with a single frequency (Fig. ii). 



. 9. - oscillograms of Oscillations i 

 E. Taylor-Jo 



I Coupled Circuits by Prof. 



The principle which underlies this method is the well- 

 known fact, to which particular attention was directed by 

 Prof. M. Wien, of Danzig, in 1906, that the damping 

 effect of very short sparks is extremely large. Hence if we 

 form a spark-gap consisting of a large number of very 

 small spark gaps in series, say ten gaps each of 03 mm., 

 and if we keep the spark surfaces cool, then not only can 

 no arc form between these surfaces, but the condenser 

 spark is immediately quenched. Moreover, if we supply 

 this spark-gap either from a high-frequency alternator or 

 from a low-pressure 

 transformer we can 

 produce as many as 

 2000 sparks per 



second. A form of 

 discharger for this 

 purpose has been de- 

 vised in Germany, 

 which consists of a 

 series of copper discs 

 or copper boxes cooled 

 with water, the flat 

 surfaces of which are 

 placed in contiguity, 

 [e^ but separated by very 

 thin rings of mica. 

 -Method of utilising waves of both The interspace be- 

 .itted by inductively-coupled tween the boxes is 

 Xransmittmg Antenna. . ..l ■ ^l. 



not more than 1/ 125th 



part of an inch, 

 and ten or twelve of these discs or boxes are placed in 

 series (Fig. 12). The row of boxes takes the place of 

 the ordinary spark balls, and is connected to the 

 secondary terminals of a transformer, fed by a high- 

 frequency alternator, and also connected to an' oscillatory 



; the delivery of this lecture, my attention has been drawn by Mr. 

 " ; bv him-elf ill the Elcctrktt' Engineer tiX October 

 cribes an almost identical arrangement devised by 

 be waves of an inductively-coupled transmitter, and 

 1 for the same purpose by Dr. Seibt. 



,1. Hettinger t 

 26, 1906, in which he Ide 

 him for capturing both I 

 refers to a prior invenlio 



circuit. When the transformer is in action it produces a 

 very large number, 1000 or more, oscillatory discharges of 

 the condenser per second, each of which has a large 

 initial amplitude, but quickly dies out. The inductively 

 or directly coupled antenna hence receives a very large 

 number of impulses per second, each of which sets up in 

 it free electrical oscillations of one definite period. 



Primary 



Secondary 



Primary 



Secondary 



Ordinary Spark 



1 I i I I I I I i 



Inductively-coupled Circuits. 



.\ discharger, composed of a single pair of metal plates 

 with interposed separating paper ring, has been devised 

 and employed by Von Lepel. In this case the plates are 

 connected to the terminals of a high-voltage direct-current 

 dynamo, and are shunted by a circuit having inductance 



Flan of Copper Flanged Plate 

 Fig. 12. — Plan and Section showing portion of Discharger. 



and capacity, one of the plates being also connected to an 

 antenna and the other to a balancing capacity. 



These discharges, however, have not stood the test of 

 prolonged practical use, and we cannot say, therefore, that 

 they are comparable in value for telegraphic purposes with- 

 the well-proved inventions of Mr. Marconi. 

 (Jo be continued.) 



NO. 2092, VOL. 82] 



