SUN AND THE EARTH'S MAGNETIC FIELD — FLEMING 179 



of the use of this property in navigation by the end of tlie twelfth 

 century A. D. 



Magnetic dip or inclination was unknown until 1581, when Eob- 

 ert Norman of London, a practical seaman and instrument maker, 

 published "The newe Attractive, containyng a short discourse of the 

 Alagnes or Lodestone, and amongest other his vertues, of a newe dis- 

 couercd secret and subtill propertie, concernyng the Declinyng of 

 the Needle, touched therewith under the plaine of the Horizon." ^ 

 Norman mounted his needle on a horizontal axle so that it was free to 

 move in the vertical plane and observed the actual dipping below 

 the horizon. This gave the first hint that the source of the mag- 

 netic field of the earth might be within the globe and not in the 

 stars as previously supposed. 



Tlience onward there was gradual transition from tlie field of spec- 

 ulation to that of scientific investigation, and in 1600 Gilbert pub- 

 lished his famous book on the magnet, the first treatise picturing the 

 earth's action as a great magnet, a conclusion which preceded New- 

 ton's announcement of universal gravitation. A century later Hal- 

 ley's world charts showing "variations" — that is, declination — of the 

 compass appeared. Wilcke's chart of magnetic dip or inclination 

 was published in 17G8. Charts delineating magnetic directive force 

 resulted fi'om Humboldt's observations on his American journeys 

 during 1799 to 1803. 



The period including the end of the eighteenth century and the 

 first half of the nineteenth century was an era of unequaled con- 

 structive work in geomagnetism by many eminent scholars. Among 

 these may be mentioned Humboklt, Gauss, and Lamont of Germany, 

 Sabine and Airy of Great Britain, Poisson and Dujjerrey of France, 

 Quetelet of Belgium, Hansteen of Norway, Kupffer of Russia, and 

 Nicollet, Locke, Loomis, Bache, and Hein*y of America. 



That thoughts on this subject were then not limited to scientific 

 men is evidenced by a discourse of John Quincy Adams in our House 

 of Representatives during preliminary steps bearing on the establish- 

 ment of the Smithsonian Institution in which he said : 



What an unknowu world of mind is yet ... to l)e revealed in tracing the 

 causes of the sympathy between the magnet and the pole — that unseen, imma- 

 terial spirit, which walks with us through the most entangled forests, over 

 the most interminable wilderness, and across every region of the pathless 

 deep, by day, by night . . . Who can witness the movements of that trem- 

 ulous needle, poised upon its center, still tending to the polar star, without 

 feeling a thrill of amazement approaching to suixjrstition? 



» In 1544 Oeorg Haitniann of Nureinburg stated he had noticed that a magnet not only 

 declines from the north and turns toward the east but also points downward. Hartmann, 

 however, did not mount his needle in sucli a manner as to show the precise amount of dip, 

 as did Norman. 



501591—43 13 



