Short Electric Waves by Air and Water-Vapour. 705 



disturbance in each tube would be confined to its own tube, 

 and act only upon its own receiver. Covering them with 

 tinfoil also got rid of disturbances due to the presence of 

 neighbouring conductors. It was found that the excitation 

 of the receivers was about five times as great when the tubes 

 were covered with tinfoil as when not covered. 



S is the sender. It consisted of two brass rods, placed end 

 to end, each 2*5 cm. long. The rods were *25 cm. in 

 diameter, rounded at the ends, and had a spark-gap '015 cm. 

 long between them. The total length of the two rods 

 together was therefore about 5 cm. It is one of the oscil- 

 lators which I have fully described in my paper on the wave- 

 length of the linear oscillator *, and it is the one that I have 

 there called the 5-cm. sender. The brass rods were supported 

 by a hard rubber cylinder, and the spark between them took 

 place in kerosene oil. The oscillator was excited by two 

 auxiliary sparks at the outer ends of the rods, each auxiliary 

 spark being about 3 mm. long. The wave-length of this 

 oscillator as previously determined f was about 10*2 cm. 



The various parts of the sender are shown in cross-section 

 in fig. 2 ; in A for a front view, and in B for a side view. 



Fig. 2. 



S" 1 B 



Sender. A, front view ; B ; side view. 



bb are the brass rods ; r, hard rubber cylinder ; cc, corks 

 closing the ends of the cylinder ; o, space filled with kero- 

 sene oil ; ss, auxiliary spark-gaps : ww, brass wires leading 

 to secondary of induction-coil ; gg, hollow glass rods sup- 

 porting these wires ; n, hard rubber rod supporting the hard 



* Physical Review, xxx. pp. 199, 200 (1910). 

 t Physical Review, xxxi. p. 214 (1910). 



