266 POPULAR LECTURES AND ADDRESSES. 



" of about two and a quarter miles ; and lastly, the 

 " declination at Kauroo Hill, about five miles N.E. 

 "of Black Cap, is 41 3' E." 1 



In virtue of the irregularities of the distribution 

 of terrestrial magnetism, rightly noticed by Gilbert, 

 but wrongly attributed to magnetic continents, and 

 mountains, and headlands, the lines of direction 

 indicated by the compass are not great circles on 

 the earth's surface, but somewhat irregular curves 

 joining the north and south magnetic poles ; and 

 the magnetic equator is not a circle, but a sinuous 

 line round the earth. 



The best information regarding the configuration 

 of these lines, at the present time, and generally 

 regarding the present condition of the earth's 

 magnetism, is to be found in the three small 

 magnetic charts showing curves of equal variation, 

 curves of equal dip, and curves of equal horizontal 

 intensity, and in the large scale Admiralty 

 Variation Chart, which have been prepared and 

 reduced to the epoch of 1871 by Captain Evans, 



1 Such a country as this submerged to eight fathoms would 

 trouble our compasses very considerably. CAPTAIN CREAK. 



