ELECTRICITY, MAGNETISM, AND QUA VI TAT JON. 



169 



hand; shaded by a pillar, goes back to zero.. At 11 a.m., 

 needle stationary, yet the sun very powerful. At lib. iOm., 

 the needle deflects 2^ to the right hand; at 3h. iJ^m., it now 

 vibrates again towards the left hand; shaded the helix, zero; 

 removed the shade, deflection V to the right hand ; it now 

 vibrates 2^ to the lefty and continues vibrating. 



II h. 20m. Begins by deflection to the right, and then in a 

 few seconds to the left, then vibrates or remains stationar}'. 



12h. 5ra. The needle is now 4i° to the right; shaded, it 

 returns ; 12h. 10m., deflection 7^° to the right hand. 



It is thus seen that the instrument, which is ordinarily 

 employed for the indication of a voltaic current, and has been 

 shown also to manifest the transition of ordinary electricity 

 and lightning, is likewise truly affected by tlie solar beams. 



That the effects upon the galvanometer are induced by solar 

 agency, is clearly manifested in the greater part of the above 

 experiments by the remarkable coincidence which is ob- 

 servable between the degrees indicated by the galvanometer 

 and the brilliancy of the solar beams, as well as by the 

 changes observed by the interposition or removal of an artifi- 

 cial screen. (See Experiments, Jan. 3rd, 6th, and 7th.) 



That the effects are not the results of thermo-electric action, 

 is evident, inasmuch as, — 



1. There has never been discovered any thermo-electric 

 phenomenon emanating from the action of heat upon any 

 simple combinations of copper ivire alone, 



2. That there was no thermo-electric influence observable 

 from the action of heat upon copper in contact tvith the 

 mercury in the mercury cup, nor upon the mercurialised ex- 

 tremity of the wire, was seen on the 6th December last ; for 

 after the removal of the mercury cup and shading the wire 

 from the sun's rays, the same results were still equally 

 observable. (See Experiment, Dec. 6.) 



3. The;-^ is no hitherto known electric, thermo-electric, or 

 voltaic action of this kind noticed in science without the 



