ST. JOHN. 



WAVE LENGTHS OF ELECTRICITY. 



245 



maximum poiut was found by 

 gradually lengthening the wire; 

 It was then found by gradually 

 shortening the wire from an 

 initial length of 60 cm. for tlie 

 sides of the rectangle. The 

 results are shown in Figure 9 

 where the upper curve is based 

 on the data found when short- 

 ening the wire, and the lower 

 on the data found when length- 

 ening it. The two differ by 

 less than a centimeter, which 

 is as near as two determina- 

 tions could be expected to agree. 

 In all determinations of the crit- 

 ical points of the curves shown, 

 reading's were taken both for- 

 ward and back, and the averages 

 used as data for the curves. 



Another result of the investigation is apparent when copper circuits 

 are compared in which wires of different diameters are used. 



3d Max G 



Copper wire, diameter 0.12010 cm. 

 " " " 0.08840 cm. 



« « " 0.07836 cm. 



'* " " 0.03915 cm. 



O 



2ry 



o 



Fig. 9. 



562.0 

 553 5 

 552.0 

 535.0 



The half wave lengths calculated from this maximum are : — 



Copper (.01201 cm.) ' 255.8 cm. 



" (.08840 cm.) 252.2 cm. 



" (.07836 cm.) 251.6 cm. 



(.03915 cm.) 244.8 cm. 



These are found by taking the total length of the circuit, and 

 dividing by 5. 



535 X 2 = 1070 cm., length of wires. 



30 cm., length of closed end. 

 62 X 2 — 124 cm., equivalent of end capacities. 



1224 cm. 

 1224 -^ 5 



244.8 cm. 



The results here presented differ from those hitherto given, and 

 particularly from those of the late Professor Hertz ; but his investiga- 



