CONTENTS. VU 



PAGE 



The explanation of this rotation . . . . . .68 



The rotation of an electrical conductor around an electrical 

 conductor 77 



A magnetic needle must arrange itself across an electrical con- 

 ductor 81 



The magnetic needle must point to the poles of the earth . 82 

 No special electrical currents in a magnet . . . ,83 

 " Magnetism" a mere mode of electrical action . . .83 



The bearing of these considerations upon the theory of elec- 

 tricity '.. ; . . . . * 'i*- "- . . 83 



As showing the presence of chemical changes in a metallic con- 

 ductor during the passage of a current . . .83 



As explaining the reason why the loadstone and steel retain 

 their "magnetic" power . . . . . . . 84 



Electrical light must be referred to chemical action . . 86 

 Electrical heat must be referred to chemical action . . .88 



The expansive effects of heat to be explained on the same 

 hypothesis 89 



The whole history of electricity points to a central law which 

 for convenience may be termed provisionally the law of the 

 laboratory . . . 92 



Character of this law of the laboratory 92 



Eeasons for supposing that this law has a wider scope than the 



laboratory . . .93 



A 4 



