4:38 Hormell — Dielectric Constant of Paraffins. 



provided it extends beyond the two wires. The balance tube 

 as well as the argon tube ought to be within at least l| cm of 

 the middle loop, otherwise the capacity effect is lessened. 



One-half of this last reading (i. e. the distance between the 

 first bridge and the second node) will give what may be called 

 the half tube wave, in which one node rests on the wires and 

 the other rests on the center of the bridge. We shall call the 

 former the wire node, and the latter the bridge node. The 

 balance tube may now be removed and the third and fourth 

 nodes located, leaving the argon tube at the first potential loop, 

 though as far as the position of the nodes is concerned the tube 

 may be placed at any other potential loop. If we add the tube 

 effect to the average reading in the second column, and also 

 the distance between the two wires, we shall get what may be 

 called a wave length in air. [To this is added also a scale cor- 

 rection of 3 mm .) This is, in fact, the length of a free wave along 

 the wires, but since the experiments of Sarasin and De La 

 Rive* have shown that the velocity of a rapidly oscillating 

 electrical disturbance along a wire is the same as that in air, 

 we have good authority for calling the above the wave length 

 in air. 



The same quantity may be secured by subtracting the first 

 reading from the third and the second from the fourth. 



Summary of the line constants. 



(1) 58-94 — 58-14 = '80 cm = tube effect. 



, x 58-14 + -3 , , 



(2) — = 29-22 cm = i tube wave. 



(3) 58-14+ 3 + '80 + 1-80 = 61-84 cm = wave length in air. 



(4) 89-49 — 27-80 =61*69 = " " 

 (5)120 61—58-94 =61*67 = " " 



61*73 = average wave length in 

 air. 



It will be seen that the wave length in air determined by 

 the first method (3) is very approximately the same as that 

 secured by the second method (4) and (5). 



(b) Determination of the Dependence of the Wave Length upon 

 the Distance between the Primary and the Secondary Coils. 



In this experiment the coils were 5 cm in diameter. The 

 primary semicircles were made of 3 mm wire and had discharg- 

 ing balls 5 mm in diameter. The pitch of the screw controling 

 the primary was l'27 mm . The primary was removed and re- 



* Archives des Sciences et Nat u relies Geneve, 1890, xxiii, p. 113. 



