MATTER AND FORCE. 63 



Sending a current through both spirals, they clash 

 suddenly together; reversing what is called the direc- 

 tion of the current in one of the spirals, they fly asun- 

 der. All these effects are due to the power which we 

 name an electric current, and which we figure as flow- 

 ing through the wire when the voltaic circuit is com- 

 plete. 



By the same agent we tear asunder the locked 

 atoms of a chemical compound. Into this small cell, 

 containing water, dip two thin wires. A magnified 

 image of the cell is thrown upon the screen before you, 

 and you see plainly the images of the wires. From a 

 small battery I send an electric current from wire to 

 wire. Bubbles of gas rise immediately from each of 

 them, and these are the two gases of which the water 

 is composed. The oxygen is always liberated on the 

 one wire, the hydrogen on the other. The gases may be 

 collected either separately or mixed. I place upon my 

 hand a soap bubble filled with the mixture of both gases. 

 Applying a taper to the bubble, a loud explosion is heard. 

 The atoms have rushed together with detonation, and 

 without injury to my hand, and the water from which 

 they were extracted is the result of their re-union. 



One consequence of the rushing together of the 

 atoms is the development of heat. What is this heat? 

 Here are two ivory balls suspended from the same point 

 of support by two short strings. I draw them thus 

 apart and then liberate them. They clash together, 

 but, by virtue of their elasticity, they quickly recoil, 

 and a sharp vibratory rattle succeeds their collision. 

 This experiment will enable you to figure to your mind 

 a pair of clashing atoms. We have in the first place, 

 a motion of the one atom towards the other a motion 

 of translation, as it is usually called then a recoil, 



