70 FARADAY 



know, from the appearance of repulsion of the pith ball at 

 the end of the straw, that electricity is present in those brass 

 conductors (BB), and I want you to see the manner in 

 which that electricity can pass away [touching the conductor 

 (B) with his finger, the lecturer drew a spark from it, and 

 the straw electrometer immediately fell]. There, it has all 

 gone ; and that I have really taken it away you shall see by 

 an experiment of this sort. If I hold this cylinder of brass 

 by the glass handle, and touch the conductor with it, I take 

 away a little of the electricity. You see the spark in which 

 it passes, and observe that the pith-ball indicator has fallen 

 a little, which seems to imply that so much electricity is lost ; 

 but it is not lost; it is here in this brass, and I can take it 

 away and carry it about, not because it has any substance of 

 its own, but by some strange property which we have not 

 before met with as belonging to any other force. Let us 

 see whether we have it here or not. [The lecturer brought 

 the charged cylinder to a jet from which gas was issuing; 

 the spark was seen to pass from the cylinder to the jet, but 

 the gas did not light.] Ah ! the gas did not light, but you 

 saw the spark; there is, perhaps, some draught in the room 

 which blew the gas on one side, or else it would light; we 

 will try this experiment afterward. You see from the spark 

 that I can transfer the power from the machine to this 

 cylinder, and then carry it away and give it to some other 

 body. 



You know very well, as a matter of experiment, that we can 

 transfer the power of heat from one thing to another ; for if 

 I put my hand near the fire it becomes hot. I can show you 

 this by placing before us this ball, which has just been 

 brought red-hot from the fire. If I press this wire to it 

 some of the heat will be transferred from the ball, and I 

 have only now to touch this piece of gun-cotton with the 

 hot wire, and you see how I can transfer the heat from the 

 ball to the wire, and from the wire to the cotton. So you 

 see that some powers are transferable, and others are not. 

 Observe how long the heat stops in this ball. I might touch 

 it with the wire or with my finger, and if I did so quickly I 

 should merely burn the surface of the skin; whereas, if I 

 touch that cylinder, however rapidly, with my finger, the 





