MODERN VIEWS WITH EESPECT TO ELECTRIC CURRENTS 655 



sides, the whole of space being agitated by the formation of an electric 

 current in any part. To show this agitation, I have here two large 

 frames with coils of wire around them. They hang face to face about 

 6 feet apart. Through one I discharge this Leyden jar, and immediately 

 you see a spark at a break in the wire of the other coil, and yet there is 

 no apparent connection between the two. I can carry the coils 50 feet 

 or more apart, and yet by suitable means I can observe the disturbances 

 due to the current in the first coil. 



The question is forced upon us as to how this action takes place. How 

 is it possible to transmit so much power to such a distance across appar- 

 ently unoccupied space? According to our modern theory of physics 

 there must be some medium engaged in this transmission. We know 

 that it is not the air, because the same effects ta,ke place in a vacuum, 

 and, therefore, we must fall back on that medium which transmits light 

 and which we have named the ether. That medium which is supposed 

 to extend unaltered throughout the whole of space, whose existence is 

 very certain but whose properties we have yet but vaguely conceived. 



I cannot, in the course of one short hour, give even an idea of the 

 process by which the minds of physicists have been led to this conclusion 

 or the means by which we have finally completely identified the ether 

 which transmits light with the medium which transmits electrical and 

 magnetic disturbances. The great genius who first identified the two is 

 Maxwell, whose electro-magnetic theory of light is the centre around 

 which much scientific thought is to-day revolving, and which we regard 

 as one of the greatest steps by which we advance nearer to the under- 

 standing of matter and its laws. It is this great discovery of Maxwell 

 which allows me, at the present time, to attempt to explain to you the 

 wonderful events which happen everywhere in space when one estab- 

 lishes an electric current in any other portion. 



In the first place, we discover that the disturbance does not take place 

 in all portions of space at once, but proceeds outwards from the centre 

 of the disturbance with a velocity exactly equal to the velocity of light. 

 So that, when I touch these wires together so as to complete the circuit 

 of yonder battery, I start a wave of ethereal disturbance which passes 

 outwards with a velocity of 185,000 miles per second, thus reaching the 

 sun in about eight minutes, and continues to pass onwards forever or 

 until it reaches the bounds of the universe. And yet none of our senses 

 inform us of what has taken place unless we sharpen them by the use of 

 suitable instruments. Thus, in the case of these two coils of wire, sus- 

 pended near each other, which we have already used, when the wave 



