SO Mr. E. H. Barton. Electrical Interference Phenomena 



Experiment VI. Analogy to Newton's Rings, as in Experiment V, but 

 with different Abnormal Part. 



Jn this experiment the lengths of SAD and the position of M were 

 precisely as in Experiment V. The abnormal part, however, con- 

 sisted simply of the ordinary wires, but put closer together there 

 than elsewhere, namely, 0'68 cm. apart instead of 8 cm. 



The electrometer readings were taken thus : First, with no ab- 

 normal part; next, with one of 0'5 m. long; again with no abnormal 

 part, then with one 1*5 m. long, and so forth. The readings with 

 and without the abnormal part were always alternated, and the ratios 

 of the throws taken as in Experiments I III. 



The result of this set of observations is graphically exhibited in the 

 curve E, fig. 5. The abscissas represent the lengths of the abnormal 



FIG. 5. Second Case of Analogy to Newton's Rings by Transmission. 



\m-. 2 3 4 5 6 7 9 JO 77*. 



of the abnormal pa,rt Of the Sesonda^ry . 



part, and the ordinates the ratios of the electrometer throws with to 

 those without it. 



Experiment VII. Analogy to Newton's Rings by Reflexion. 



In this experiment the arrangement of apparatus shown in fig. 1 

 was modified by removing the electrometer from EE' and inserting it 

 at HH', where HB is a quarter of a wave's length. Throughout the 

 experiment the lengths were as follows : 



SAD = 235 mm., SAB = 164 mm. 



The abnormal part was of tinfoil sheets, 32 cm. deep and 50 cm. 

 long, precisely as in Experiment V, while the end BB' remained fixed, 

 the length BC was varied from nothing to 6 m., advancing by steps 

 of half a metre. 



The electrometer throws were taken, first with a bridge at BB', 

 then without the bridge but with an abnormal part consisting of a 



