156 ANNUAL OF SCIENTIFIC DISCOVERT. 



composition, are divided, so far as their thermo-electric relations 

 arc concerned, into two ji;roiips. Calling tiie two forms of the 

 minerals a and b, Mar!)ach j^ives the following series, reckoning 

 from negative to positive : Iron jn'rites, a ; cobaltine, a; bismuth, 

 German silver, platinum, lead, copper, brass, silver, cadmium, 

 iron, antimony cobaltine, 6; iron pyrites, 6. — Pogg. Ann., April, 

 1865, as quoted in American Joicrnal of Science, September, 1805. 



A NEW AND POWERFUL THERMO-ELECTRIC BATTERY. 



In a communication to the Vienna Academy, dated March 16, 

 1865, S. Marcus di'.scril)t'd a nmv thermo-electric battery, which 

 possesses extraordinary interest, botli in a theoretical and practi- 

 cal point of view. The properties of the new battery are as 

 follows : — 



1. The electro-motive force of one of the new elements is equal to 

 l-2oth of tiiat of a Bunsen's clement of zinc and carbon, and by 

 its internal resistance is equal to 0.4 of a meter of normal wii-e, 



2. Six such elements are suJlieient to decomiJose acidulated water. 



3. A battery of 125 elements evolved in 1 minute 25 cubic cen- 

 timetres of mixed oxygen and hydrogen, although decomposition 

 took place under disadvantageous circumstances, as the internal 

 resistance of the battery was much greater tlian that of the 

 voltameter in the circuit. 4. A jjlatinum wire of ^ millimeter in 

 thickn(!ss, introduced into the circuit, melted. 5. Thirty elements 

 develop in an electi-o-magnet a lilting power of 150 pounds. 6. 

 The current is generated by warming only one of the contact 

 sides of the elements, antl cooling the other, by means of water 

 of the ordinary temperature. 



As positive metal in tliese batteries, Marcus employs an alloy 

 of 10 parts of co])per, 6 of zinc, and 6 of nickel. The addi- 

 tion of 1 part of cobalt increases the electro-motive force. For 

 the negative metal lie uses an alloy of 12 jiarts of antimony, 5 

 of zinc, and 1 of bismuth. The electro-motive force of the alloy is 

 increased Ijy repeated fusion. In place of these alloys, a partic- 

 idar kind of Germ.an silver, known as alpacca, may be used with 

 the same negati\ e metal ; or, as the positive metal, an alloy of 65 

 parts of copper and 31 of zinc, and, as the negative metal, an 

 alloy of 12 parts of antimony and 5 parts of zinc. The bars are 

 not soldered but screwed together. The mechanical arrangement 

 is such that only tlie positive metal is directly heated, the negative 

 metal being warmed by conduction; the former melts at about 

 1200° C, the latter at about 600° C. 



An interesting fact in relation to the transformation of heat into 

 electricity in the thermo-electric battery, is, that the water wliieh 

 serves to cool one of the contact sides of each element, becomes 

 very slowly warmer so long as the circuit remains closed, but is 

 heated pretty rapidly when the circuit is open. The alloys em- 

 plo3-ed in this battery fulfil several conditions essential to the pro- 

 duction of powerful electrical currents by heat. These conditions 

 are, that the metals employed should be as far as possible from 

 each other in the thermo-electric series ; that they should permit 



