(56 Chant — Variation of Potential along a 



table by more prominent type, will be referred to as the chief 

 minimum. 



In fig, are shown readings and curves obtained with the 

 20°'" oscillator with various lengths of wire, and in fig. 10 are 

 similar readings with the oscillator of double the size, i. e., 

 with -i0 cm plates; while in fig. 11 is shown a series of three 

 successive curves given by the 20 cm oscillator with the same 

 length of wire. These illustrate the method moderately well. 



Remarks on the Table and the Curves. — A glance at the 

 table will show that the oscillators used can be divided into 

 two distinct groups, the first including the four smaller ones, 

 and the second the three larger ones, while the oscillator with 



30 cm plates lies between the two groups. The results with 

 each group are consistent among themselves, while the 30 cm 

 oscillator behaved in a very irregular manner. 



For the first group (the smaller ones), the positions of the 

 minima for any particular length of wire are independent of 

 the size of the oscillator, i. e., they depend only on the wire's 

 length. In this case the oscillator does not force its period on 

 the wire. 



In the second group, on the other hand, the positions of the 

 minima depend only on the size of the oscillator, not at all on 

 the length of the wire. 



The conclusion seems natural that, in this latter case, the 

 distance of the minimum from the free end is one-quarter of 

 the wave-length of the oscillating system. The values of this 

 quarter-wave-length deduced from the table are : 



For 35 cm oscillator 132'7 cms (mean of 11 results). 



" 40 " 147*1 " 21 



« 50 " .... 171-5 " 6 " 



