126 COSMOS. 



Europeans could not have learnt, from their own expe- 

 rience, the direction of the magnetic needle in the southern 

 hemisphere before the second half of the 15th century, when 

 they may have obtained an imperfect knowledge of it from 

 the adventurous expeditions of Diego Cam with Martin 

 Behaim, and Bartholomew Diaz, and Vasco de Gama. The 

 Chinese, who, as early as the 3rd century of our era, as well 

 as the inhabitants of Corea and the Japanese Islands, had 

 guided their course by the compass at sea, no less than by 

 land, are said, according to the testimony of their earliest 

 writers, to have ascribed great importance to the south direc- 

 tion of the magnetic needle, and this was probably mainly 

 dependent on the circumstance, that their navigation was 

 entirely directed to the south and south-west. During these 

 southern voyages, it had not escaped their notice that the 

 magnetic needle, according to whose direction they steered 

 their course, did not point accurately to the south pole. We 

 even know, from one of their determinations, the amount ^ of 

 the variation towards the south-east, which prevailed during 

 the 12th century. The application and farther diffusion of 

 such nautical aids favoured the very ancient intercourse of 

 the Chinese and Indians with Java, and to a still greater 

 extent the voyages of the Malay races and their colonisation 

 of the island of Madagascar. 81 



1845, Results, pp. 2 7. It is singular to find that the position of the 

 needle during the first period from April to October (western min. 

 7h. 30m. A.M., max. Oh. 30m. P.M. ; min. 5h. 30m., max. 7 P.M.) coin- 

 cides so closely with that of Central Europe. The month of October is 

 a transition period, as the amount of diurnal variation scarcely amounts 

 to 2 minutes in November and December. Notwithstanding that this 

 station is situated 8 from the magnetic equator, there is no obvious 

 regularity in the turning hours. Everywhere in nature, where various 

 causes of disturbances act upon a phenomenon of motion at recurring 

 periods (whose duration, however, is still unknown to us), the law by 

 which these disturbances are brought about often remains for a long 

 time unexplained in consequence of the perturbing causes either reel- 

 procally neutralising or intensifying one another. 



60 See my Examen Grit, de I'ffist. de la Geogr. t. iii, pp. 3437. 

 The most ancient notice of the variation given by Keutsungchy, a writer 

 belonging to the beginning of the twelfth century, was east J- south. 

 Klaproth's Lettre sur I' invention de la Boussole, p. 68. 



61 On the ancient intercourse of the Chinese with Java, according to 

 Btatements of Fahian in the Fo-kue-si, see Wilhelin von Huraboldt, 

 Ueber die Kawi Spracke, Bd. i, s. 16. 



