II. 



ELECTRICAL IlIIEOMETRY. 



43 



with regard to the cahmLations. The fi)llowuig tables contain the results of the 

 experiments, made with a deviation between 3U and 35 degrees. 



Table A. — Containing (lie Iniensifi/ of Action of the Currents surrounding the Globes, 

 tvhen the Needle ivas j^luccd on the Fhlar Diameter. 



Position of 

 needle. 



Series A. 

 Tot. resist, at 

 centre 28.91 



B. 



35.5 



C. 



3r).2 



D. 



28.2 



E. 

 21.3 



Common 

 means. 



Difference between 



the maximum and 



niiiiiinum. 



centre. 



1.000 



1.000 



1.000 



1.000 



1.000 



1.000 



1.000 



2 tenths. 



1.043 



1.057 



1.029 



1.018 



1.042 



1.036 



0.039 



4 " 



1.14S 



1.194 



1.142 



1.100 



1.147 



1.158 



0.052 



G " 



1.409 



1.428 



1.387 



1.422 



1.406 



1.411 



0.041 



7 " 



1.C71 



1.002 



1.585 



1.0)3 



1.6C6 



1.642 



0.080 



8 " 



2.125 



2.112 



2.029 



2.003 



2.136 



2 093 



0.007 



9 " 



3.170 



3.228 



3.228 



3.173 



3.133 



3.180 



0.115 



9.2 " 



3.308 



3.42 



3.793 



3.854 



3.332 



3.541 



0.546 



It appears from this table that the values of the ratios of forces are less than we 

 have found for the circle. These observations, though made on angles, a little 

 different from one another, give results whose difference is not beyond the limits of 

 the errors of observation, as appears from the column of differences, except in the 

 last line of 9.2 ; both from a little variation of position which could not be accu- 

 rately measured, and the inllucnce of a smaller distance, the differences are 

 considerable. 



We have already spoken, in the preceding section, of the difficulty met with in 

 the determination of the true centre of action inside the wires crossing at tiie poles. 

 In order to appreciate, by means of the experiments, the difference arising from 

 different suppositions on this point, we made two series of observations ; in one we 

 reckoned for the length of the radius of the globe, the distance of the centre from 

 the inner layer of the wires, and in the other that from the most external one. 

 The results were as follows : — 



Table B. 



Position of 



Reckoning from the inside. 



Reckoning from the outside. 



f'oinmon 



needle. 



Ist series. 



2d series. 



8d series. 



4th series. 



IliLMlIlH. 



centre. 



1.000 



1.000 



1.000 



l.OOl) 



1.000 



6 



1.355 



1.362 



1.394 



1.545 



1.416 



7 



1.591 



1.5.52 



1.694 



1.790 



1.656 



8 



1.975 



1.978 



2.288 



2.410 



2.162 



9 



2.904 



2.895 



3.434 



3.640 



3.215 



