Jan. 19, 1855.] Prof. Faraday on Magnetic Philosophy. 7 



cases before the contemplative mind. Thus, if a metallic vessel, as 

 an ice-pail, be insulated and connected with a delicate gold leaf 

 electrometer, or other like instrument, and then an insulated 

 metallic globe, half the diameter of the ice-pail, be charged with 

 positive electricity and placed in the middle of the pail, the latter 

 being for the moment uninsulated by a touch outside, and then 

 left insulated again, the whole system will show no signs of electri- 

 city externally, nor will the electrometer be affected : but a carrier 

 applied to the ball within the vessel will bring away from it positive 

 electricity, showing its particular state of charge ; or being applied 

 to the lower inside surface of the vessel will bring away negative 

 electricity, proving that it has the contrary state : or the duality 

 may be proved by withdrawing the ball, when the vessel will show 

 itself negative by the electrometer, and the ball will be found 

 positive. That these dualities are equal, is further shown by replac- 

 ing the ball within the vessel, observing the electrometer, bringing 

 tlie ball and vessel in contact, and again observing the electrometer, 

 which will remain unchanged ; and finally withdrawing the ball, 

 which comes away perfectly discharged, and leaves the vessel exter- 

 nally in its unchanged and previous state. So the electric dualities 

 are equal, equivalent, and mutually sustained. To show that one 

 cannot exist alone, insulate the metallic vessel, charge it strongly by 

 contact with the machine or a Leyden jar, and then dip the insulated 

 ball into it ; and after touching the bottom of the vessel with the 

 ball, remove it, without touching the sides : it will be found 

 absolutely free from charge, whatever its previous state may have 

 been ; for none but a single state can exist at the bottom of such a 

 metallic vessel ; and a single state, i.e. an unrelated duality, cannot 

 exist alone. 



The correspondent dualities, i.e. the northness and the southness, 

 of the magnetic force are well known. For the purpose of insulat- 

 ing, if possible, one of these, and separating it in any degree from 

 the other, numerous experiments have been made. Thus six equal 

 electro-magnets, formed of square bars, were put together in the 

 direction of three lines perpendicular to each other, so that their 

 inner ends, being all alike in polarity, might inclose a cubical space 

 and produce an experimental chamber. When excited, these 

 magnets were very powerful in the outer direction, as was found by 

 nails, filings, spirals, and needles ; but within the chamber, walled 

 in on every side by intense north poles, there was no power of any 

 kind : filings were not arranged ; small needles not affected, except 

 as they by their own inducing powers caused arrangement of the 

 force within ; revolving wire helices produced no currents ; the 

 chamber was a place of no magnetic action. Ordinary magnetic 

 poles of like nature produced corresponding results. A single pole 

 presented its usual character, attracting iron, repelling bismuth ; a 

 like pole, at right angles to it, formed a re-entering angle, and there 

 a weak place of magnetic action was caused ; ifon was attracted from 



