BATTERIES. 



71 



Marcus, but he has selected, as a second metal, iron in 

 preference to copper, as the former is more lasting. 



We illustrate (Fig. 9) the model of a diamond battery 

 which we had occasion to use in 1875 for actuating a small 

 Gramme machine. 



This battery consists of 10 elements circularly arranged, 

 and therefore possesses ten bars of Marcus alloy connected 



FIG. 9. 



diamond Thermo-Electric Battery. 



together by means of thin sheets of iron offering externally a 

 large surface to the cooling action of the atmosphere. The 

 even soldered joints are at the centre, and the odd ones outside 

 the apparatus. 



Such a battery, for example, composed of 5 crowns of 

 10 couples each, regularly deposits 20 grammes of copper per 

 hour, with an expenditure of 170 litres of gas (6 cubic feet), 

 which corresponds, as we have seen, to an intensity of about 

 17 amperes. If we admit a total electromotive force of half a 



