PRESIDENTIAL ADDRESS. LXVII 



ir their latest works on meteorology, Milham and Moore, follow- 

 ing Hann, show a spiral movement for the poleward seeking air 

 as it moves from the high pressure belts. The fact that volcanic 

 dust, as that from the great eruption of Krakatoa in 1883, after 

 rising to a height of what is estimated to have been over 23 miles, 

 became distributed practically over the atmosphere of the whole 

 world suggests that probably poleward seeking and spirally moving 

 air currents actually exist. According to Dr. Shaw's theory, there 

 might still presumably be a slow interchange of air between the 

 poles and the high pressure belts through the " passing-on " action 

 of the Antarctic cyclones, just as a football is passed to and fro 

 in a series of " scrums " on a football field. As far as the obser- 

 vations of the members of tlie Shackleton expedition extend, the 

 high level circulation near the South Pole from the Antarctic 

 Circle polewards has a distinct southerly component of movement. 

 After encountering intensely severe westerly gales on the Nimrod 

 we suddenly emerged into clear weather near the Antarctic Circle, 

 and for two days obtained good observations of cirrus clouds float- 

 ing at an altitude of between 15,000 and 18,000 feet. These were 

 moving towards a direction between S.E. and E.S.E., at an 

 approximate speed of about 20 miles an hour. At our winter 

 quarters at the foot of Mt. Erebus, we were almost exactly due 

 west of that mighty active volcano, so that we were in an admir- 

 able position to see, by means of the deflection of the great steam 

 column at its summit, whether or not there was any southerly 

 component in the atmosphere at a level of over 13,000 feet. Nor- 

 mally, when the volcano was in only mild eruption, the steam cloud 

 was slightly deflected to the north of east by an air current blowing 

 from off the high plateau. ^ On the whole this wind, therefore, 

 appeared to be an equator-seeking wind, part of a return current 

 from the pole towards the belt of the Antarctic " lows." At the 

 same time it may have been merely a local wind blowing from the 

 high plateau to the Ross Sea, whicli is not only a low-lying area, 

 but an area of low pressure also. Now comes a point which appears 

 of special interest. On the 14th June, 1908, an eruption of con- 

 siderable violence broke out from the summit of Erebus. Vast 

 volumes of steam rose in globular masses so rapidly above the 

 active crater that in about a couple of minutes they attained an 

 altitude of from 5,000 to 6,000 feet above the summit of the 

 mountain — that is, they rose at the rate of about half-a-mile a 

 minute. The spectacle was truly sublime; but the most thrilling 

 moment oF all was when, as the top of the steam cloud rose above 

 the 15,000-ft. limit, it was suddenly deflected by a very powerful 

 and rapid overhead current having a very decided southerly com- 

 ponent. Long wreaths of white vapour were quickly trailing out 



' The direction of the mstrugi (\\ind-eroded furrows) on the plateau to the west of the 

 Royal Society Range, as observed by Scott, are from W. by S., or W.S.W., to E. by N., or 

 E.N.E. 



