THE CORRELATION OF THE PHYSICAL FORCES 79 



table. We need do no more than just bring these two ends 

 in contact, when the spark shows us what power is present; 

 and what a strange thing it is to see that this force is 

 brought away from the battery behind me, and carried along 

 through these wires! I have here an apparatus (Fie. 46) 

 which Sir Humphrey Davy constructed many years ago, in 

 order to see whether this power from 

 the voltaic battery caused bodies to 

 attract each other in the same manner 

 as the ordinary electricity did. He 

 made it in order to experiment with 

 his large voltaic battery, which was 

 the most powerful then in existence. 

 You see there are in this glass jar 

 two leaves of gold, which I can cause 

 to move to and fro by this rack-work. 

 I will connect each of these gold 

 leaves with separate ends of this 

 battery, and if I have a sufficient 

 number of plates in the battery, I 

 shall be able to show you that there 



will be some attraction between those leaves even before 

 they come in contact; if I bring them sufficiently near 

 when they are in communication with the ends of the battery, 

 they will be drawn gently together ; and you will know when 

 this takes place, because the power will cause the gold leaves 

 to burn away, which they could only do when they touched 

 each other. Now I am going to cause these two leaves of 

 gold to approach gradually, and I have no doubt that some 

 of you will see that they approach before they burn, and 

 those who are too far off to see them approach will see by 

 their burning that they have come together. Now they are 

 attracting each other, long before the connection is complete, 

 and there they go ! burnt up in that brilliant flash, so strong 

 is the force. You thus see, from the attractive force at the 

 two ends of this battery that these are really and truly 

 electrical phenomena. 



Now let us consider what is this spark. I take these 

 two ends and bring them together, and there I get this 

 glorious spark like th sunlight in the heavens above us. 



