CHEMISTRY 91 



thing like the quadrilHonth of a pound. This force may ap- 

 pear excessively small but as a matter of fact it is enormous. 

 It is more than a trillion trillion times (10^^ times) greater 

 than gravitational attraction, which accounts for the weight 

 of bodies on the earth's surface and the motion of the heavenly 

 bodies. How enormous it is may be realized from the fol- 

 lowing imaginary experiment. Let two masses, say, of lead 

 weighing 1 gram each be placed one centimeter apart. They 

 will attract each other with a force of 6.6 x 10"^ dynes, a 

 force quite too small to be measured by any known instru- 

 ment. But now let 2 grams of pure negative electricity, "elec- 

 trons", be placed side by side at the same distance. They 

 would repel each other with a force of 31.4 x 10^* dynes or 

 320 quadrillion tons! Even if they were placed, one at the 

 north pole of the earth and the other at the south pole, they 

 would still repel each other with a force of 192 million tons 

 and that in spite of the fact that the force decreases with 

 the square of the distance. The force would be capable of 

 imparting to each of these grammes of pure electricity a veloc- 

 ity equal to that of light in less than a millionth of a second 

 and would only fail to do so owing to the fact that the inertia 

 of each electron becomes infinite or nearly so as it approaches 

 the velocity of light. 



Suppose there to be only 1 gram of pure electricity, and 

 a single electron placed at 1 centimeter from it. The force 



is still 194 million dynes, about -y- of a ton. If the electron 

 were removed as far as the sun the force exerted by 1 gram 

 of pure electricity on the earth upon all the free electrons 

 in the sun would suffice to impart to them a velocity equal 

 to that of light in 20 seconds. 



So much for the electron, the negative electric charge. 

 What about the positive charge? Speaking of this, the posi- 

 tive unit of electricity. Sir Joseph Thomson says: 



"Does, or does not, this unit differ, in size and physical 



