42 



RESEARCHES ON 



II. 



N. B. It may be seen from this last, which is a repetition of the first (except a 

 slight difference in the deviation), that the results agree well together when found 

 with the same initial resistance, but there is a little difference when that is a good 

 deal greater. Tlie errors of observation cannot be more than Voth in the ratio of 

 the highest positions, which is partly due to the unavoidable errors arising from a 

 little aberration in the position of the globe, as we have already stated, but there 

 is also some other reason, which we shall discuss hereafter. 



We add here two series more of experiments, made in different days, each one 

 of which is the mean of two series made immediately the one after the other. 



Fourth Series 





Fifth Series. 



Position of 



Total 



Ratios of 



Total 



Ratios of 



noodle. 



rosistiiiico. 



rosistanoes. 



resistance. 



resistances. 



centre. 



57.08 



1.000 



87.25 



1.000 



2 tenths. 



58.35 



1.022 



89.85 



1.025 



4 " 



7i.;$8 



1.2(i8 



99.85 



1.144 



6 " 



84..58 



1.481 



119.35 



1.367 



7 " 



101.28 



1.774 



149.25 



1.009 



8 " 



129.58 



2.270 



200.25 



2.282 



9 " 



210.48 



3.087 



359.05 



4.103 



Constant resistance of the fourth series 



" " of the fifth " 



Deviation of needle, fourth series 

 " " fifth " 



TURNS. 



57.08 



87.85 



30° 10' 



18° 02' 



§ 10. Experiments with the Globe, and their Results. 



The globe has already been described, § 8. The manner of conducting the 

 experiments was the same as Avith the circle, but the deviations, of the needle were 

 not so accurately measured. This, however, malies but little difference when the 

 degrees are about 25 and 30, as appears from the experiments of the circle. We 

 must- therefore allow something in the results for this inaccuracy, particularly as 

 the experiments were made with great care in all other things. We shall enlarge 

 upon the experiments here, since their comparison with our theory seems very 

 interesting, and demands a new series of experiments to be made on a larger scale. 



In investigating the action on the vortical diameter, the numbers found with the 

 globe are not very far from those obtained with the circle ; now this conclusion was 

 already deduced from the theory, and thus we have here also a confirmation of 

 our formuUx), in another general case. 



The small difforonco observed between the circle and the globe arises from this : 

 that the condition of a very small noodle in comparison with the circle is not 

 wholly fulfilled, and thus the function Z being smaller for the extreme circles, the 

 total action must be less than if the circles were in the magnetic meridian. 



Should I be able to repeat them again, I shall then enter into further details 



