VI 



LIST OF ILLUSTRATIONS. 



Page. 



Illustration of surface tension of electricity .... 342 



Saussure's electroscopic explorer ..... 3.51 



Use of Saussure's electroscopic explorer (2 figs.) . . . 352 



Induction from the earth shown by insulated vertical rod . . 352 



Dellman's apparatus for exhibiting atmospheric electricity . . 354 



Peltier's electrometer ....... 355 



Changed sign of induced electricity at different heights . . 356 



Hour-glass appearance of thunder-cloud .... 360 



Illustration of remarkable induction effect from distant lightning . 369 



Oersted's deflection of magnetic needle hy galvanic current . . 427 



Magnetization of iron-filings by galvanic current . . . 427 



Arrago's method of magnetizing sewing-needles, &c. . . 428 



Sturgeon's first horse-shoe electro-magnet .... 429 



Improvement of the horse-shoe magnet (First "intensity " magnet) . 429 



Magnet of compound helices (Improved " quantity " magnet) . 430 



Electro-magnetic bell signal at Albany in 1831 . . . 434 



