[ 105 ] 



Report on the State of our Knowledge respecting the Magnetism 

 of the Earth. By S. Hunter Christie, Esq., M.A., F.R.S. 

 M.C.P.S., Corr. Memb. Philom. Sac. Paris, Hon. Memh. 

 Yorkshire Phil. Soc; of the Royal Military Academy ; and 

 Member of Trinity College, Cambridge. 



Had the discovery of the loadstone's dh'ective power been made 

 by a philosopher who at the same time pointed out its import- 

 ance to the purposes of navigation, we might expect that his 

 name would have been handed down to posterity as one of the 

 greatest benefactors of mankind. The discovery was, however, 

 most likely made by one so engaged in maritime enterprise that, 

 in his eyes, this application constituted its whole value ; and it 

 is not improbable that, being for some time kept secret, it may 

 have been the principal cause of the success of many enterprises 

 attributed to the superior skill and bravery of the leaders. The 

 knowledge of this property of the magnet, though gradually 

 diffused, would long be guarded with jealousy by those who 

 justly viewed it as of the highest advantage in their predatory 

 or commercial excursions ; and this is, perhaps, the cause of the 

 obscurity in which the subject is veiled. If the discovery is 

 European, there is no people, from the character of their early 

 enterprises, and, I may add, from the nature of the rocks of 

 their country, more likely to have made it than the early Nor- 

 wegians ; and as there is reason for believing that they were 

 acquainted with the directive property of the loadstone at least 

 half a century earlier than its use is supposed to have been 

 known in other parts of Europe, it may be but justice to allow 

 them the honour of having been the discoverers. Whether the 

 discovery was made in Asia or in Europe, in the North or in 

 the South, I am not, however, now called upon to decide, but 

 to point out the consequences which have followed that disco- 

 very by unveiling gradually phaenomena, though less striking, 

 yet equally interesting, and some even more difficult of expla- 

 nation. 



These phaenomena are, the variation of the magnetic needle, 

 with its annual and diurnal changes ; the dip of the needle ; and 

 the intensity of the magnetic force of the earth; which are, how- 

 ever, all comprised under two heads, — The Direction and the 

 Intensity of the terrestrial magnetic force. 



