



THE SIZE OF ATOMS. 205 



p. 157). A simple harmonic motion is, as you now 

 see sustained by my hand in the uppermost bar, 

 in a period of about four seconds. You see that 

 a regular wave-motion travels down the line of 

 molecules represented by these circular disks on 

 the ends of the bars, and the energy continually 

 given to the top bar, by my hand, is continually 

 consumed in heating the basin of treacle and 

 water at the foot. I now remove my hand and 

 leave the whole system to itself. The very con- 

 siderable sum of kinetic and potential energies 

 of the large masses and spiral springs, attached 

 to the top bar, is gradually spent in sending the 

 diminishing series of waves down the line, and is 

 ultimately converted into heat in the treacle and 

 water. You see that about half of the amplitude 

 of vibration, and therefore three-fourths of the 

 energy, is lost in half a minute. 



You will see on quickening the oscillation how 

 very different the result will be. The quick oscilla- 

 tions which I now give to the top bar (the period 

 having been reduced to about one and a half 

 seconds), is incapable of sending wavss along the 



