50 COSMOS. 



The ancient Greeks and Romans were acquainted with the 

 adhesion of iron to the magnet, attraction and repulsion, and 

 the transmission of the attracting action through brass ves- 

 sels as well as through rings, which were strung together in a 

 chain-like form, as long as one of the rings was kept in con- 

 tact with the magnet ; M and they were likewise acquainted 

 with the non-attraction of wood and of all metals excepting 

 iron. The force of polarity, which the magnet is able to 

 impart to a moveable body susceptible, of its influence, was 

 entirely unknown to the Western nations (Phoenicians, Tus- 

 cans, Greeks, and Romans). The first notice which we meet 

 with among the nations of Western Europe of the knowledge 

 of this force of polarity, which has exerted so important an 

 influence on the improvement and extension of navigation, 

 and which, from its utilitarian value has led so continuously 

 to the inquiry after one universally diffused, although pre- 

 viously unobserved force of nature, does not date farther back 

 tliMitho llth and 12th centuries. In the history and enu- 

 meration of the principal epochs of a physical contempla- 

 tion of the universe, it has been found necessary to divide 

 into several sections, and to notice, the sources from which 

 vre derive our knowledge of that which we have here sum- 

 marily arranged under one common point of view. 53 



We find that the application amongst the Chinese of the 

 directive power of the magnet, or the use of the north and 

 south direction of magnetic needles floating on the surface of 

 water, dates to an epoch which is probably more ancient 

 than the Doric migration and the return of the Heraclidse 

 into the Peloponnesus. It seems, moreover, very striking 

 that the use of the south direction of the needle should have 

 been first applied in Eastern Asia not to navigation but to 

 land travelling. In the anterior part of the magnetic waggon 

 a freely floating needle moved the arm and band of a small 

 figure, which pointed towards the south. An apparatus of 

 this kind (called fse-nan, indicator of the south,) was pre- 



52 The principal passage referring to the magnetic chain of rings 

 occurs in Plato's Ion. p. 533, D.E ed. Steph. Mention has been made 

 of this transmission of the attracting action not only by Pliny (xxxiv, 

 14) and Lucretius (vi, 910), but also by Augustine (de civitate Dei, 

 xx, 4) and Philo (de Mwndi opificio, p. 32 D ed. 1691). 



53 Cosmos, vol. i, p. 182 ; vol. ii, p. 628. 



