LECTURE V 



MAGNETISM ELECTRICITY 



I WONDER whether we shall be too deep to-day or not. 

 Remember that we spoke of the attraction by gravitation 

 of all bodies to all bodies by their simple approach. Re- 

 member that we spoke of the attraction of particles of the 

 same kind to each other that power which keeps them to- 

 gether in masses iron attracted to iron, brass to brass, or 

 water to water. Remember that we found, on looking into 

 water, that there were particles of two different kinds at- 

 tracted to each other; and this was a great step beyond the 

 first simple attraction of gravitation, because here we deal 

 with attraction between different kinds of matter. The hy- 

 drogen could attract the oxygen and reduce it to water, but 

 it could not attract any of its own particles, so that there 

 we obtained a first indication of the existence of two 

 attractions. 



To-day we come to a kind of attraction even more curious 

 than the last, namely, the attraction which we find to be of a 

 double nature of a curious and dual nature. And I want, 

 first of all, to make the nature of this doubleness clear to 

 you. Bodies are sometimes endowed with a wonderful at- 

 traction, which is not found in them in their ordinary state. 

 For instance, here is a piece of shellac, having the attraction 

 of gravitation, having the attraction of cohesion, and if I 

 set fire to it, it would have the attraction of chemical affinity 

 to the oxygen in the atmosphere. Now all these powers we 

 find in it as if they were parts of its substance ; but there is 

 another property which I will try and make evident by means 

 of this ball, this bubble of air [a light India-rubber ball, 

 inflated and suspended by a thread]. There is no attraction 

 between this ball and this shellac at present ; there may be a 

 little wind in the rooms slightly moving the ball about, but 



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