SCIENCE AND MAX. 343 



Grove's battery, zinc is consumed in acidulated water; 

 and in the battery we are able so to arrange matters that 

 when no current passes no zinc shall be consumed. Now 

 the current, whatever it may be, possesses the power 

 of generating heat outside the battery. We can fuse 

 with it iridium, the most refractory of metals, or we 

 can produce with it the dazzling electric light, and that 

 at any terrestrial distance from the battery itself. 



We will now, however, content ourselves with caus- 

 ing the current to raise a given length of platinum 

 wire, first to a blood-heat, then to redness, and finally 

 to a white heat. The heat under these circumstances 

 generated in the battery by the combustion of a fixed 

 quantity of zinc is no longer constant, but it varies in- 

 versely as the heat generated outside. If the outside 

 heat be nil, the inside heat is a maximum; if the ex- 

 ternal wire be raised to a blood-heat, the internal heat 

 falls slightly short of the maximum. If the wire be 

 rendered red-hot, the quantity of missing heat within 

 the battery is greater, and if the external wire be ren- 

 dered white-hot, the defect is greater still. Add to- 

 gether the internal and external heat produced by the 

 combustion of a given weight of zinc, and you have an 

 absolutely constant total. The heat generated without 

 is so much loss within, the heat generated within is so 

 much lost without, the polar changes already adverted 

 to coming here conspicuously into play. Thus in a 

 variety of ways we can distribute the items of a never- 

 varying sum, but even the subtle agency of the electric 

 current places no creative power in our hands. 



Instead of generating external heat, we may cause 

 the current to effect chemical decomposition at a dis- 

 tance from the battery. Let it, for example, decompose 

 water into oxygen and hydrogen. The heat generated 

 in the battery under these circumstances by the com- 



