268 POPULAR LECTURES AND ADDRESSES. 



point of the compass card, he will be led to a point 

 in about 146 of .east longitude, and 73 south 

 latitude. This point is the earth's south magnetic 

 pole. The diagram shows just two magnetic poles, 

 and if, as is probably the case, it is approximately 

 correct in the hitherto unexplored polar regions, 

 Halley's celebrated hypothesis of four magnetic 

 poles is disproved for the present time. But the 

 dotted lines in the neighbourhood of the 

 astronomical north and south poles are drawn 

 conjecturally, and some degree of straining, 

 particularly in the north polar region, is required 

 to bring them all to pass through the points 

 marked on the chart as the north and south 

 magnetic poles. There is indeed a somewhat 

 determined tendency of the lines in the explored 

 regions of from 145 to 150 east longitude, to 

 converge towards a point in the unexplored sea 

 north of Siberia in about 105 east longitude, and 

 80 north latitude, and it seems therefore not im- 

 possible that there is in reality a north magnetic 

 pole in that region. As for the points marked as 

 north and south magnetic poles on the chart, the 



