328 THERMO-ELECTRICITY. SECT. XXXIV- 



discovered that electric currents may be produced by 

 the partial application of heat to a circuit formed of two 

 solid conductors. For example, when a semicircle of 

 bismuth, joined to a semicircle of antimony, so as to form 

 a ring, is heated at one of the junctions by a lamp, a 

 current of electricity flows through the circuit from the 

 antimony to the bismuth, and such thermo-electric cur- 

 rents produce all the electro-magnetic effects. A com- 

 pass needle placed either within or without the circuit, 

 and at a small distance from, it, is deflected from its na- 

 tural position, in a direction corresponding to the way in 

 which the electricity is flowing. If such a ring be sus- 

 pended so as to move easily in any direction, it will obey 

 the action of a magnet brought near it, and may even 

 be made to revolve. According to the researches of M. 

 Seebeck, the same substance, unequally heated, exhibits 

 electrical currents ; and M. Nobili observed, that in all 

 metals, except zinc, iron, and antimony, the electricity 

 flows from the hot part toward that which is cold. That 

 philosopher attributes terrestrial magnetism to a differ- 

 ence in the action of heat on the various substances of 

 which the crust of the earth is composed ; and in con- 

 firmation of his views he has produced electrical currents 

 by the contact of two pieces of moist clay, of which one 

 was hotter than the other. 



M. Becquerel constructed a thermo-electric battery of 

 one kind of metal, by which he has determined the re- 

 lation between the heat employed and the intensity of 

 the resulting electricity. He found that in most metals 

 the intensity of the current increases with the heat to a 

 certain limit, but that this law extends much farther in 

 metals that are difficult to fuse, and which do not rust. 

 The experiments of Professor Gumming show that the 

 mutual action of a magnet and a thermo-electric current 

 is subject to the same laws as those of magnets and gal- 

 vanic currents, consequently all the phenomena of repul- 

 sion, attraction, and rotation maybe exhibited by a thermo- 

 electric current. M. Botto, of Turin, has decomposed 

 water and some solutions by thermo-electricity ; and 

 very recently the Cav. Antinori of Florence has suc- 

 ceeded in obtaining a brilliant spark with the aid of an 

 electro-dynamic coil. 



