ANTARCTIC EXPLORATION. 301 



one of the problems awaiting solution . Whatever its nature may be, 

 the area is so large and so near to us that its meteorology must have a 

 dominant influence on the climate of Australia, and on this fact the 

 value of a knowledge of the weather of these parts must rest. 



To turn to another branch of science, there are several questions re- 

 lating to the earth's magnetism which require for their solution long- 

 maintained and continuous observations within the Antarctic circle. 

 The mean or permanent distribution of the world's magnetism is be- 

 lieved to depend upon causes acting in the interior of the earth, while 

 the periodic variations of the needle probably arise from the superficial 

 and subordinate currents produced by the daily and yearly variations in 

 the temperature of the earth's surface. Other variations occur at irregu- 

 lar intervals, and these are supposed to be due to atmospheric electricity. 

 All these difi"erent currents are excessively frequent and powerful about 

 the poles, and asuflScient series of observations might enable physicists 

 to differentiate the various kinds of currents, and to trace them to their 

 several sources, whether internal, superficial, or meteoric. To do this 

 properly at least one land observatory should be established for a period. 

 In it, the variation, dip, and intensity of the magnetic currents, as well 

 as the momentary fluctuations, of these elements would all be recorded. 

 Fixed term days would be agreed on with the observatories of Australia, 

 of the Cai)e, America, and Europe, and during these terms a concerted 

 continuous watch would be kept up all round the globe to determine 

 which vibrations were local and which general. 



The present exact position of the principal south magnetic pole has 

 also to be fixed, and data to be obtained from which to calculate the 

 rate of changes in the future, and the same may be said of the foci of 

 magnetic intensity and their movements. In relation to this part of the 

 subject. Captain Creak recently reported to the British Association his 

 conclusions in the following terms. He says : " Great advantage to the 

 science of terrestrial magnetism would be derived from a new magnetic 

 survey of the southern hemisphere extending from the parallel of 40° 

 south, as far towards the geographical pole as possible." 



Intimately connected with terrestrial magnetism are the phenomena 

 of auroras. Their nature is very obscure, but quite recently a distinct 

 advance has been made towards discovering some of the laws which 

 regulate them. Thanks to the labors of Dr. Sophus Tromholt, who 

 has spent a year within the Arctic circle studying them, we now know 

 that their movements are not as eccentric as they have hitherto ap- 

 peared to be. He tells us that the Aurora Borealis, with its crown of 

 many lights, encircles the pole obliquely, and that it has its lower edge 

 suspended above the earth at a height of from 50 to 100 miles, the mean 

 of 18 trigonometrical measurements, taken with a base line of 50 miles, 

 being 75 miles. The aurora forms a ring round the pole which changes 

 its latitude four times a year. At the equinoxes it attains its greatest 

 distance from the polcj and at midsummer m^ midwinter it approacli^f? 



