Electric Waves along Wives. 



GG1 



each change seemed to show that the frequency of the 

 primary was slightly less when the bridges were very near 

 than when at a considerable distance from each other, but the 

 change in the position of the bridge KK' for syntony only 

 amounted to 2 or 3 mm., and as this was within the limits of 

 possible error, absolute certainty on the point was impossible. 

 It was, however, too small to affect the results obtained. It 

 should be noticed that the proximity of the wires of the 

 primary to the secondary circuit would affect the period of 

 the secondary in the same way as the secondary wires would 

 affect the primary, but the alteration in the period of the 

 primary would be double that of the secondary, and conse- 

 quently would make itself felt by the change in the length of 

 the secondary necessary to give perfect resonance. 



The conclusion from these two experiments is that the 

 period remained practically constant throughout the changes 

 in the secondary. Another question which arose was whether 

 or not the position of the bridge giving the maximum intensity 

 of oscillation was the position in each case wmich made the 

 circuit KBxB/Jx 7 an exact wave-length corresponding to the 

 period of the primary. In the case of stout wires a wave 

 traverses the circuit with very slight diminution of intensity ; 

 consequently increasing or decreasing the length of that 

 circuit by a small amount has very little effect on the intensity 

 of the wave after once traversing the circuit. When wires of 



high resistance are used, a small change in the length f the 



. . . ° 



circuit may alter the intensity of the wave after completing 



the circuit by an appreciable amount, i. e. by the amount due 



to the damping by that length of wire by which the circuit is 



lengthened or shortened. 



Let a be the amplitude of a wave starting at the end BxB/, 



ae 2 its amplitude when at R, 



_3Ax 



ae 2 its amplitude when at R again, and so on ; 



where x is the length of a double circuit of 

 parallel wires necessary to produce the diminu- 

 tion of intensity which the wave experiences in 

 once traversing the circuit. 



When the secondary is in tune with the primary, if we 

 take the amplitude of oscillation at any instant as the sum of 

 the amplitudes of the damped pulses which would be induced 

 separately by the various oscillations in the primary, the 

 expression for this amplitude, n complete periods after the 



