23 



CHAPTER IV. 



ON HEAT PRODUCED BY THE MAGNETIC OR GALVANIC 



FLUID. 



The next phenomenon which a battery displays is the power 

 of heating substances according to the amount of current which 

 is actually passing, and the resistance which they afford to its 

 passage ; and in this way the most infusible metals, as platinum, 

 palladium, gold, copper, iron and steel, may be instantly melted. 



Conducting liquids may be heated in a similar manner. This 

 fact may be seen in a great variety of ways : dilute sulphuric 

 acid may be made to boil in a siphon connecting two vessels, in 

 which the poles of an extensive series of batteries are placed. 

 Another mode of showing the same fact is to take a piece of 

 string and moisten it with acid, connecting the extremities with 

 the poles of a series of galvanic batteries, when it will begin to 

 smoke, and become charred from the heat produced. 



The next property which a battery displays is its power of 

 igniting metallic or charcoal points when joined to the two ends 

 of the battery, and held so that they barely touch ; a light is 

 then exhibited equal in brilliancy to that of a little sun. The 

 spark seems to depend principally upon a combustion of fine 

 particles of metal, and, when charcoal or hard gas coke is used, 

 upon little points of it flying from one pole to the other ; so that 

 one pole wastes away and the other increases, till the flame be- 

 comes quite encased in a mass of carbonaceous matter. This 

 flame is singularly repelled or attracted by a magnet held in its 

 vicinity. Heat is, indeed, one of the effects of chemical action ; 

 and though we might by a fallacious reasoning be led to assert 

 that chemical action is the effect of heat, a very slight examina- 

 tion will show the absolute futility of such reasoning. In fact, 

 we have no heat of which the cause is known, but that which 

 is derived from, and proportionate to, chemical action. 



When we observe a body of water, we may with propriety 

 state that it was derived from the ocean ; but we could not be 

 justified in attributing a similar origin to fire, or in stating that 



