352 NINETEENTH CENTURY, pt. hi. 



on this principle that the induction-coil is made which is 

 now used to increase the power of the electricity coming 

 from an electric battery; 



Professor Seebeck discovers Thermo-electricity, or the 

 Production of Electricity by Heat. — The fact was now 

 clearly established that electric and magnetic currents move 

 at right angles to each other, and this gives to a certain 

 extent the answer to our question. Why does a magnet 

 turn to the north? Ampere suggested quite early in the 

 discussion, that if an electric current will turn metals into 

 magnets, the electric currents which we know are flowing 

 from east to west round our globe, may turn the earth 

 (which is full of metals) into a great magnet. But it is 

 also true that exactly the opposite efifect is possible, and that 

 the magnetic currents may be started by some other cause 

 and may set up the electric currents, so that we do not 

 really know which gives rise to the other. 



An interesting discovery was, however, made in 1822 

 by Professor Seebeck, showing a possible cause of the 

 electric currents flowing from east to west. He wished to 

 try whether he could not give rise to a current of electricity 

 in two metals by merely using heat instead of acid and 

 water. For this purpose he took a half ring of copper and 

 fastened to it a bar of a metal called antimony, so that the 

 two metals had the form of a stirrup, and inside this stirrup 

 he hung a magnetic needle, which would show if any 

 current passed along the metals. Then he heated one of 

 the corners where the metals joined, and immediately the 

 magnet began to turn, showing that an electric current was 

 passing through the copper, and back through the antimony. 

 He tried this with many other metals, and in every case 

 when one of the parts where they joined was made hotter 



