MAGNETISM AND ELECTRICITY. 1638 
chemically pure condition, but also gold, silver, platinum, and other metals. 
More recently the various operations of gilding, silvering, plating, &c., 
have been carried to great perfection and into new applications by the 
electrotype. For full details on this interesting subject we would refer our 
readers to the various works of Smee, GC. V. Walker, Becquerel, and 
others. 
As electricity exercises a chemical action, so it may be proved that any 
chemical combination or decomposition developes electricity. The 
combustion of carbon may serve as an illustration, where the carbonic acid 
produced is positively electric, while the carbon itself is negative. To 
prove this, take a suitable cylindrical piece of charcoal, and stand it upon 
a long brass plate (pl. 22, fig. 13), attached to one plate of a condenser. 
Set the coal on fire and keep up a vigorous combustion by means of a pair 
of bellows ; on connecting the lower plate of the condenser with the earth 
the whole apparatus will soon be charged with negative electricity. To 
collect the positive electricity, place the charcoal on a plate in 
communication with the earth, and hold it under the above-mentioned 
brass plate. 
The physical effects of the galvanic current consist partly in the 
development of light and heat, partly in the exhibition of magnetic 
phenomena. Oersted first suggested the intimate connexion between 
magnetism and electricity, by his discovery that a freely suspended 
magnetic needle is deflected whenever it is brought near the terminating 
wire of a battery in full action. Electricity at rest or in a state of great 
tension does not produce this phenomenon. The experiment is best 
performed in the following manner: Form a rectangle of eight or ten 
inches in diameter out of a strong copper wire (pl. 20, jig. 68), bring its 
plane into that of the magnetic meridian, and connect the extremities of 
the wire, ab and fg, with the poles of a battery of large surface. If ab be 
connected with the positive. and fg with the negative pole, the positive 
current will circulate in the direction of the arrows. Now, if a magnetic 
needle be held above the branch cd, the north pole will be deflected towards 
the east, and towards the west when held below cd. The action will be 
precisely the reverse at the branch ef. To assist the memory in recollecting 
the various directions of deflection under different circumstances, Ampére 
has suggested the following method: A little human figure is imagined as 
attached to any one branch of the wire, with the positive current always 
passing in at the feet and out at the head. The figure being supposed 
always to have its face turned towards the needle, the deflection of the 
north pole will ever take place towards its left hand. 
The multiplier or galvanometer of Schweigger depends for its principle 
upon this deflecting power of the galvanic current in the various forms of 
this instrument, this power being increased by multiplying the windings of 
the wire. All the portions of the galvanic current which pass in the 
direction of the arrows of the elongated rectangle (p/. 20, fig. 69) act in 
the same direction upon the inclosed magnetic needle; if then a wire pass 
round the needle in, say 100 turns, all traversed by the same current, 
ICONOGRAPHIC ENCYCLOP£DIA.—VOL. I. 22 337 
