SECT. IT. ELECTRICITY. 31 



with the solar spots. Professor Lamont of Munich 

 has discovered that a permanent and regular current 

 of electricity is propagated parallel to the equator all 

 over the earth, and another similar to it in the atmo- 

 sphere. Besides these, there are currents of electricity 

 in the surface of the earth, sometimes in one direction 

 and sometimes in. another, which decrease with the 

 depth ; and M. Lamont conceives that this electric 

 system is the cause of terrestrial magnetism. Elec- 

 tricity of intense power and inappreciable quantity 

 certainly exists in abeyance in the atmosphere and 

 in all terrestrial matter till the equilibrium between 

 the antagonist forces be disturbed, and then it bursts 

 forth with terrific violence in the lightning flash and 

 stunning crash of thunder. Since it requires elec- 

 tricity equivalent to that in activity during a thunder- 

 storm to form one drop of water, what must that 

 power have been which, the Omnipotent wielded when 

 he created that deep over the face of which ' darkness 

 brooded.' 



Electricity, though the most formidable power 'in 

 nature, is made available to man by the voltaic battery, 

 and by the electro-magnetic induction apparatus, in 

 the battery of which it is generated by the chemical 

 action of dilute sulphuric acid on zinc. The positive 

 and negative electricities thus produced pass in opposite 

 directions through the two conducting wires of the 

 machine by a continuous transmission of force or vibra- 

 tion from atom to atom, a circulation that is accompanied 

 by a continual development of heat in overcoming the 

 resistance it meets with in the wires. The electricity 

 decreases as the heat increases, and vice versa; the 

 action is reciprocal. Thus electricity is merely a trans- 

 mission of force. Mr. Joule has proved that the 

 quantity of heat produced in a unit of time is propor- 



