somewhat analogous to Newton s Rings. 



77 



without any tinfoil sheets on the wires, then a couple of readings 

 with, say, two sheets on each wire ; then two readings with four 

 sheets on each wire, and so forth. After the abnormal part had thus 

 been built up to a considerable length, it was then in like manner 

 shortened, two readings being taken for each length, concluding with 

 several readings without any sheets at all on the wires. T-he whole 

 process was carried out four times, the lengths used in the various 

 cases being varied so as to obtain eight electrometer readings for 

 each half metre's length of the abnormal part. Thus, in the first and 

 third sets of observations, the lengths of the abnormal part were 



approximately 0, 1 m., 2 m., 3 m 3 m., 2 m., 1 m., ; whereas, 



in the second and fourth sets, the lengths were about 0, 0'5 m., 1'5 m., 

 2'5 m 2'5 m., 1*5 m., O5 m., 0. 



A single set of readings up to nearly 7 m. length of abnormal part 

 is given in Table II. During the process of lengthening the abnormal 

 part, the ratios are obtained by taking for the divisor the initial mean 

 throw without abnormal part, whereas, during the shortening, the 

 like final value is used as the divisor. Hence the double values for 

 the ratio corresponding to the length 6'72 m. The last column of 

 the table contains the mean of the ratios during lengthening and 

 shortening. 



The kind of agreement obtained by the four sets of observations is 

 shown by the two curves in fig. 3. In these curves the abscissae 



FIG. 3. Preliminary Curves from Experiment Y. 



1-0 



u i m.. co oo 



Lengths of the abnormal part of tli& Secondary 



represent the lengths of the abnormal part. In the upper curve the 

 ordinates represent the lengths of the abnormal part. In the upper 

 curve the ordinates represent the mean ratios of the throws obtained 

 the first and third sets of observations with and without the 



in 



abnormal part. The ordinates of the lower curve give the values of 

 the same ratios, as obtained from the second and fourth sets of 

 readings. 



