92 CORRELATION OF PHYSICAL FORCES. 



take place in the cells of the battery a definite quantity of 

 zinc being dissolved and of hydrogen eliminated in a given 

 time. If now the platinum wire be immersed in water, the 

 heat will, from the circulating currents of the liquid, be more 

 rapidly dissipated, resistance in the wire is lessened, and we 

 shall instantly find that the chemical action in the battery will 

 be increased, more zinc will be dissolved, and more hydrogen 

 eliminated for the same time ; the heat being conveyed away 

 by the water, more chemical action is required to generate it, 

 just as more fuel is required for boiling in proportion as evapo- 

 ration is more rapid. 



Reverse the experiment, and instead of placing the wire 

 in water, place it in the flame of a spirit-lamp, so that the 

 force of heat meets with greater resistance to its dissipation. 

 We now find that the chemical action is less than in the first 

 or normal experiment. If the wire be placed in other different 

 gaseous or liquid media, we shall find that the chemical 

 action of the battery will be proportioned to the facility with 

 which the heat is circulated or radiated by these media, and 

 we thus establish an alternating reciprocity of action between 

 these two forces : a similar reciprocity may be established be- 

 tween electricity and motion, magnetism and motion, and so 

 of other forces. If it cannot be realised with all, it is pro- 

 bably because we have not yet eliminated interfering actions. 

 If we carefully think over the matter, we shall, unless I am 

 much mistaken, arrive at the conclusion that it cannot be 

 otherwise, unless it be supposed that a force can arise from 

 nothing can exist without antecedent force. 



In the phenomenon of the voltaic arc, the electric spark, 

 &c., to which I have already adverted, electricity directly pro- 

 duces light of the greatest intensity of any artificially obtained. 

 It directly produces magnetism, as shown by Oersted, who first 

 distinctly proved the connection between electricity and mag- 

 netism. These two forces act upon each other, not in straight 

 lines, as all other known forces do, but in a rectangular direc- 

 tion ; that is, bodies affected by dynamic electricity, or the 

 conduits of an electric current, tend to place magnets at 

 right angles to them ; and, conversely, magnets tend to place 

 bodies conducting electricity at right angles to them. Thus an 



