ILLUSTRATIONS
Reading edition
The double pivoted needle of Petrus Peregrinus 17
First pivoted compass, Peregrinus, 1269 19
Magnetic Declination at New York 21
" " " San Francisco 21
" " in London, in 1580 and 1907 23
First dip-circle, invented by Norman in 1576 29
Norman's illustration of magnetic dip 31
Gilbert's orb of virtue, 1600 32
Behavior of compass-needle on a terrella or spherical lodestone 44
Gilbert's "versorium" or electroscope 69
Gordon's electric chimes, 1745 75
Modern form of Leyden jar, with movable coatings 87
Three coated panes in series 89
" panes in parallel 89
" jars in parallel 90
" jars in cascade 90
Discharge by alternate contacts 94
Tassel of long threads or light strips of paper 101
Procopius Divisch (1696-1765) 108
The Divisch lightning conductor (1754) 111
Set of pointed rods 112
Galvani (portrait) opposite page 133
Volta " " " 162
Oersted " " " 205
The Magnetic effect of an electric current 209
Magnetic field surrounding a conductor carrying a current 212
Magnetic whirl surrounding a wire through which a current is passing 213
Ampère's molecular currents 214
The "sympathetic telegraph" from Cabeo's Philosophia Magnetica, 1629 216
The "sympathetic telegraph" from Turner's Ars Notoria, 1657 218
Ampère (portrait) opposite page 232
Faraday " " " 299
Clerk Maxwell (portrait) opposite page 334
Lord Kelvin " " " 361