MR. DANIELL ON VOLTAIC COMBINATIONS. 43 



When connexion was made at the same time with both hemispheres, the deviation 

 was the same. If, while in this state, either wire were lifted singly from its connexion, 

 the needle remained perfectly steady. 



When the wire from the zinc ball was lifted from the cup, there was a spark upon 

 breaking the circuit ; and there was also a spark when the wires from the two hemi- 

 spheres were disconnected from the circuit together, but not when lifted singly. 



Upon leading the conducting wire of the lower hemisphere into direct communi- 

 cation with that of the zinc ball, while the wire of the upper hemisphere was connected 

 as before with the galvanometer, or vice versa, the needle only receded to 40°. From 

 this it appeared that, although the whole amount of force originating at the zinc was 

 capable of passing off by means of either hemisphere singly, when both passages were 

 open it distributed itself between the two, notwithstanding the additional resistance 

 in one by the interposition of the galvanometer. 



Extra contacts made with different parts of the two hemispheres made no differ- 

 ence in any of the preceding experiments. 



The apparatus was now left for eighteen hours with both hemispheres in connexion 

 with one extremity of the galvanometer, and the zinc ball with the other. Upon ex- 

 amination the needle was found still deflected 25° ; and upon agitation of the zinc 

 ball it rose to 55°, but almost immediately declined to 25°. The acid had become 

 nearly saturated with oxide of zinc. The sphere was opened, and both hemispheres 

 exhibited a perfectly even coating of beautiful pink copper, through which the rings 

 of the upper hemisphere were however still discernible. 



It will perhaps be advantageous, before I proceed further, to collect into one point 

 of view the principal conclusions which, I conceive, may be drawn from the preceding 

 experiments with the spherical combination. 



1st. The force emanating from the active zinc centre diffused itself over every part 

 of the upper hemisphere, from which there was a good conducting passage for its cir- 

 culation, to an amount which is measured by 60° of the galvanometer; and which was 

 capable of maintaining an inch of platinum wire -j-i-g- inch diameter at red heat. 



2nd. The same amount of force was maintained by either hemisphere indifferently ; 

 but when both conducting hemispheres were in metallic communication there was 

 no increase of force. The transfer of half the power from one hemisphere to the 

 other occupied no appreciable interval of time. 



3rd. Although the force was not increased it spread itself equally over the whole 

 sphere, as manifested by the diffusion of the precipitated copper. 



4th. When one hemisphere was connected with the zinc centre by a short wire 

 capable of affording circulation to the whole force, and the other hemisphere was 

 connected by a long wire through the galvanometer with the same centre, the diffu- 

 sion of the force over the whole sphere was maintained, although the half of it was 

 obliged to overcome the much greater resistance of the longer circuit. 



5th. There was no greater accumulation of precipitated copper about the points 



G 2 



