EXPLANATION OF ELECTRICITY 



go on spinning for hours, so perfectly are they 

 poised. But throw on the " load," and a power of 

 fifty thousand horse is consumed in keeping them 

 going. Yet to the eye there has been no visible 

 change; simply a shunt current has been sent 

 through the coils of the dynamos and made of these 

 inert masses of steel powerful magnets. To whirl 

 the armatures in this magnetic "field" now re- 

 quires tremendous power. What, then, are the 

 armatures doing? They touch nothing. They 

 are simply cutting the invisible "lines of force" 

 which radiate through the field, and it is doing this 

 work which constitutes the so-called "load." They 

 are cutting paths through an invisible something 

 which lies beyond human ken, but which is never- 

 theless as real as the waters through which the 

 Deutsckla\id ploughs its way ; and some of its prop- 

 erties are measurable. 



It was clear enough that any theory of elec- 

 tricity must take into account all these relations 

 between the "fluid" and magnetism; and here 

 Franklin's notions seemed rather crude. More- 

 over, the curious fact that light and electricity 

 travel at the same unthinkable speed readily sug- 

 gested that there might be intimate relations be- 

 tween these two sets of phenomena as well. Mean- 

 while, in the domain of optics, some novel con- 

 ceptions had surged. 



135 



