132 THE EEASON -WHY. 



"He made darkness his secret place : his pavilion round about him were dark 

 waters and thick clouds of the skies. 



565. Why does the rubbing of a stick of sealing-wax cause 

 it to attract small particles of matter ? 



Because it excites in the sealing-wax that force which was first 

 observed in the amber. Sealing-wax, therefore, is called an electric 

 (amber-like) body. 



566. Why do we hear of the electric fluid? 



Simply because the term fluid is the most convenient that can be 

 found to express our ideas when speaking of the phenomena of 

 electric force. But of the nature of electricity, except through its 

 observed effects, nothing is known. 



567. What substances are electric ? 



All substances in nature, from the metals to the gases. But 

 they differ very widely in their electrical qualities. 



568. What is positive electricity? 



Electricity, when it exists, or is excited, in any body, to an 

 amount which is in excess of the amount natural to that body, is 

 called positive (called also vitreous). 



569. What is negative electricity ? 



Electricity, when it exists, or is excited, in any body, in an 

 amount which is less than is the amount natural to that body, is 

 called negative (called also resinous). 



570. Why is "positive" electricity called also <f vitreous." 

 and "negative" electricity called also "resinous "? 



Because some philosophers believe that there is but one elec- 

 tricity, but that it is liable to variations of quantity or state, 

 which they distinguish by positive and negative; while other 

 philosophers believe that there are two electricities, which they 

 name vitreous and resinous, because they may be induced 

 respectively from vitreous and resinous substances, and they dis- 

 play forces of attraction and repulsion. 



571. Upon what do the electrical phenomena of nature 

 Depend ? 



Upon the tendency of electricity to find an equilibrium between 

 its positive and negative states (assuming there to be but ojie fluid) ; 



