GILBERT'S THEORY OF THE LODESTONE. 287 



that period. On the contrary such a rise is apt to be de- 

 termined by a comparatively few salient achievements, 

 which being more readily appreciated and understood than 

 others, are more promptly turned to useful account. In 

 every stage of the world's progress the making of discov- 

 eries "ahead of the times" has been going on ; and of 

 these perhaps the greater proportion remain mere items of 

 abstract knowledge for years, perhaps for centuries, until 

 thought advancing to new points of view so discerns their 

 practical utility : or some keener intellect sees in them 

 possible applications to which other minds have been 

 blind. It will be apparent therefore that in tracing his- 

 torically such an intellectual rise as is here chronicled, a 

 more or less arbitrary selection must be exercised, and 

 matters often in themselves important, but which appear 

 to exert no active influence thereupon, must be omitted. 

 Otherwise the work reduces itself to the gathering of 

 chronological annals. 



After having declared the origin and nature of the lode- 

 stone on the strength of initial experiments, which, how- 

 ever he interpreted them, were in fact drawn mainly from 

 Peregrinus, Gilbert takes up the problem of the iron 

 magnet; forliere was plainly a substance having the prop- 

 erties of the lodestone and yet differing from that primary 

 terrene Matter, although of like Form or vigor. He 

 evolves the theory that the earth gives forth humors or 

 exhalations, which coalesce with solid materials to form 

 metals, and, if these materials be the more homogeneous 

 or internal Matter of the globe, the result is iron or lode- 

 stone, which is nothing but a noble iron ore ; if they be 

 the globe Matter, in an altered or baser state, or efflor- 

 escences, then other metals are produced. Iron ore is, 

 therefore, the homogenic telluric body to which the earth 

 humor has been added ; but the latter does not destroy the 

 potency of the earth-Form existing therein, and hence it 



