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OUR PHYSICAL WORLD 



rod bears at the end opposite its fellow a metallic knob; these 

 knobs, by the adjustment of the rods, may be spaced as desired. 

 As a current flows in the coarse wire of the induction coil, it 

 induces a high-tension current in the fine wire coil. Electrons 

 then discharge on to one set of sheets of foil in the condenser, 

 say the set connected with the aerial. These repel similar charges 



FIG. 113. Diagram of a more complex sending outfit 



on the other set of sheets, and drive them off at the same time 

 they draw up positive charges from the earth on to them. Such 

 positive charges help hold more electrons on the first set which 

 draw more positive charges to the second set. This " condensa- 

 tion" continues until a strong charge of high- voltage electricity 

 accumulates, when finally there is a discharge back and forth 

 across the gap, and simultaneously the current surges up into 

 the antenna and sets going radio waves in the ether. 



