256 



SCIENCE. 



[Vol. XVI. No. 405 



but that it is only 28 at the south (Maury's Meteorology, p. 

 259). In other words, the Antarctic Circle is permanently 

 much harer of atmosphere than any other part of the globe. 

 Again, if we consult a wind-chart, we shall see that both 

 jjoles are marked as calm areas. Each is the dead centre of 

 a perpetual wind-vortex, but the south-polar indraught is 

 the stronger. Polarward winds blow across the 45th degree 

 of north latitude for 189 days in the year, but aci'oss the 45th 

 degree of south latitude for 209 days. And while they are 

 drawQ in to the north pole from over a disk-shaped area 

 5,500 miles in diameter, the south-polar indraught is felt 

 throughout an area 7,000 miles across. Lastly, the winds 

 :which circulate about the south pole are more heavily charged 

 with moisture than are the winds of corresponding parts of 

 -the other hemisphere. Now, the extreme degree in which 

 these three conditions — of a perpetual grand cyclone, a moist 

 .atmosphere, and a low barometer — co-operate without the 

 Antarctic, ought to produce within it an exceptional meteoro- 

 logical state; and the point to be determined is, what that 

 condition may be. Maury maintained that the conjunction 

 will make the climate of the south-polar area milder than 

 that of the north. His theory is, that the saturated winds, 

 being drawn up to great heights within the Antarctic, must 

 then be eased of their moisture, and that simultaneously they 

 must disengage vast quantities of latent heat; and it is be- 

 cause more heat must be liberated in this manner in the 

 louth-polar regions than in the north, that he infers a less 

 severe climate for the Antarctic. He estimates that the re- 

 sultant relative differences between the two polar climates 

 will be greater than that between a Canadian and an English 

 -winter (Maury's Meteorology, p. 466). Ross reports that 

 the south-polar summer is rather colder than that of the 

 north, but still the southern winter may be less extreme, and 

 so the mean temperature may be higher. If we examine 

 the weather reports logged by Antarctic voyagers, iostead of 

 the temperature merely, the advantage still seems to rest 

 with the south. In the first place, when the voyager enters 

 the Antarctic, he sails out of a tempestuous zone into one 

 of calms. To cemonstrate the truth of this statement, I 

 have made an abstract of Ross's log for the two months of 

 January and February, 1841, which he spent within the 

 Antarctic Circle. To enable every one to understand it, it may 

 be well to explain that the wind-force is registered in figures 

 from 0, which stands for a dead calm, up to 12, which repre- 

 sents a hurricane. I find that during these 60 days it never 

 once blew with the force 8; that is, a fresh gale. Only twice 

 did it blow forceL?, and then only for half a day each time. 

 Force 5 to 6 — fresh to strong breezes— is logged on 21 days. 

 Force 1 to 3 — that is, gentle breezes— prevailed on 34 days. 

 The mean wind-force registered under the entire 60 days was 

 3.43; that is, only a four to five knot breeze. On 38 days 

 blue sky was logged. They never had a single fog, and on 

 11 days only was it even misty. On the other hand, snow 

 fell almost every second day. We find such entries as these : 

 "Beautifully clear weather," and " Atmosphere so extraor- 

 dinarily clear that Mount Herschel, distant 90 miles, 

 looked only 30 miles distant." And again, "Land seen 120 

 miles distant, sky beautifully clear." Nor was this season 

 exceptional, so far as we can tell; for Dr. M'Cormack, of the 

 *' Erebus," in the third year of the voyage, and after they 

 liad left the Antarctic for the third and last time, enters in 



his diary the following remark. He says. " It is a curious 

 thing that we have always met with the finest weather 

 within the Antarctic Circle; clear, cloudless sky, bright sun, 

 light wind, and a long swell" (M'Cormack's Awto?'cfic Voy- 

 age, V. i. p. 345). It would seem as if the stormy wester- 

 lies, so familiar to all Australian visitors, had given to the 

 whole southern hemisphere a name for had weather, which 

 as yet, at least, has not been earned by the south-polar re- 

 gions. It is probable, too, that the almost continuous gloom 

 and fog of the Arctic (Scoresby's Arctic Regions, pp. 97 and 

 137) in July and August have prejudiced seamen against the 

 Antarctic summer. The true character of the climate of this 

 region is 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 knowl- 

 edge of the weather of these parts must rest. 



To turn to another branch of science, there are several 

 questions relating to the earth's magnetism which require 

 for their solution long-maintained and continuous observa- 

 tions within the Antarctic Circle. The mean or permanent 

 distribution of the world's magnetism is believed 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 sur- 

 face. Other variations occur at irregular intervals, and 

 these are supposed to be due to atmospheric electricity. All 

 these different currents are excessively frequent and power- 

 ful about the poles; and a sufficient 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 cur- 

 rents, as well as the momentary fluctuations of these ele- 

 ments, would all be recorded. Fixed term days would be 

 agreed on with the observatories of Australia, of the Cape, 

 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 move- 

 ments. In relation to this part of the subject, Capt. Craik 

 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 dis- 

 covering some of the laws which regulate them. Thanks to 

 the labors of Dr. Sophus Tromholdt, 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 

 appeared to be. He tells us that the Aurora Borealis, with 

 its crown of many lights, encircles the pole obliquely, and 



