September 22, 1923] 



NA TURE 



437 



south polar area, being a land surface, is entirely 

 dependent on snowfall for its glaciation, and the 

 snowfall there is comparatively small, if only on 

 account of the low vapour content of the air in very 

 tcold regions. Yet in spite of the exposure of the 

 [high plateau to six months' continuous summer 

 sunshine, except in so far as clouds may sometimes 

 lobscure it, the cold continues so intense as to preserve 

 fthe ice-sheet intact. In the first place, it must be 

 [■remembered that the Antarctic Plateau, though 

 extensive, is small enough to be chilled in the same 

 way as any other mountain uplift in any latitude 

 rising like an island into the cold of the free atmosphere, 

 which is not effectively heated by the sun's rays 

 traversing it. In the second place, the snow-surface 

 reflects so much of the incident solar radiation that 

 comparatively little is available for raising the tem- 

 perature of the snow to melting-point. These two 

 factors account for the severe summer cold of the 

 Antarctic Plateau ; but if the major factor were 

 removed, that is to say, if the plateau, retaining its 

 present horizontal extent and its present amount of 

 snowfall, were lowered to sea-level, it is probable, 

 as Stefansson thinks, that the ice-sheet would dis- 

 appear in summer, permitting grass, or even spruce 

 forest, to flourish, just as in the Arctic lowlands 

 to-day. 



That a reduction to sea-level of the Antarctic 



Plateau would remove the permanent ice-cap is the 



^opinion, moreover, of Messrs. Priestley and Wright, 



expressed in the handsome volume on the glacio- 



)gy of the second Scott expedition (1910-1913), 



fhich. has just been published. I do not, however, 



illy support Dr. Stefansson in expecting that a 



lowland south polar continent surrounded by an 



^ce-chilled ocean would be liable, at least so often, 



to the high summer temperature of the Arctic low- 



' mds, and for this reason. In the Arctic lowlands of 



'anada or Siberia hot spells in June and July may 



)e materially assisted by the passage northward of 



Jair heated in the continental regions to the south, 



ind on the contrary cool spells with summer frosts 



lay be occasioned by northerly winds off the ice- 



shilled polar sea. 



Dr. Stefansson has pointed out in his letter of 



lugust 4 that the temperature is invariably lowered 



in hot summer .spells in the Mackenzie Valley, as 



compared with places in Alaska, in consequence of a 



persistent polar wind which blows up that valley. 



low this polar wind up the Mackenzie valley in hot 



i^eather is just a local monsoon effect created by the 



reat difference of temperature between the heated 



ind and chilly ocean, and is precisely the pre- 



lominant type of circulation one would expect to 



)e set up by a lowland south polar continent heated 



)y summer sunshine and encircled by an ice-chilled 



:ean. Instead of the present glacial anticyclone 



nth outflowing winds, inflowing winds chilled by 



;a-ige would commonly flow in towards the lowland 



intarctic continent and bring a good deal of cloud, 



rain or sleet, so that the occasions when high-air 



temperatures of 80° to 90° F. could occur during the 



)uthern midsummer, December and January, would 



)e less frequent than in the circumpolar Arctic 



^lowlands in the northern midsummer, June and 



July, and confined to calm clear conditions. 



As regards the dependence of Arctic spruce forest 

 on a short hot summer. Dr. Stefansson makes clearer 

 in his " Northward Course of Empire " than in his 

 letter of August 4, that a factor of enormous im- 

 portance in high latitudes is the constant summer 

 daylight. As a bioclimatic factor, light is equally 

 important with warmth, and it is apt to be overlooked 

 by climatologists that the contrast between summer 



and winter is just as much one of light and darkness 

 as of heat and cold in middle latitudes and much 

 more so in polar latitudes. Now it was shown so 

 far back as 1893 that in cold latitudes plants require 

 and utilise more diffuse daylight than in warm lati- 

 tudes. In the Arctic lands not only is the period of 

 continuous, or nearly continuous, daylight much 

 longer than the period of high temperature which is 

 limited to a few weeks, but on account of the low 

 altitude of the sun the ratio of diffuse to direct 

 sunlight is much greater than in the tropics, so that 

 the intensity of diffuse daylight is relatively great, and 

 there can be no doubt that this factor is all-important 

 in permitting vegetation to push much farther north 

 than would be the case if light were not able to 

 some extent to replace warmth in the economy of 

 plants during the Arctic summer. 



The " Northward Course of Empire," reviewed in 

 Nature of June 23, p. 839, by Dr. H. R. Mill, was 

 written to correct exaggerated views concerning the 

 inhospitality of the " Frozen North," and to show 

 the possibility of settlement in the Arctic lowlands. 

 Many interesting philosophical questions are raised 

 therein. For example, if Dr. Stefansson 's generalisa- 

 tion is sound to the effect that the negro, beset on 

 all sides by terrible parasitic enemies, can move to 

 the Arctic and remain healthy if suitably protected 

 from the cold, whereas the more robust Eskimo 

 immediately sickens and dies of germ infections if 

 brought south, because in the comparatively germ-free 

 atmosphere of the far north he has developed no 

 resisting power, the thoughtful reader will inquire 

 whether the high and increasing degree of protection 

 from infection which modern hygiene and medicine 

 is affording to civilised races is not being purchased 

 at the expense of that resisting power which enabled 

 them to survive the ignorance and dangers of the 

 past, so that dire results might follow any temporary 

 withdrawal of the protecting hand through some 

 emergency. At all events, it is clear that a sound 

 medical philosophy will have an eye to the dangers 

 of coddling no less than to those of undue exposure 

 to adverse agencies. L. C. W. Bonacina. 



27 Tanza Road, Hampstead, N.W.3, 

 August 29. 



NO. 2812. VOL. 1 12] 



Series Spectra in Oxygen and Sulphur. 



A FEW months ago I wrote a paper (Abstract, 

 Physical Review, 21, 710, 1923) on " New Series 

 Spectra in Oxygen." It was read at the meeting of 

 the American Physical Society in Washington, D.C., 

 last April. Some questions arose there concerning 

 these series because of their rather unusual character. 

 Hence I re-photographed the spectra of oxygen and 

 obtained data that confirm and extend my earlier 

 results. I also studied the element sulphur, which 

 resembles oxygen in its spectroscopic properties, and 

 obtained, for the first time I think, sulphur spectra 

 in the region of wave-lengths shorter than X2500. 



Oxygen. — The new series reported at Washington 

 have been extended from two to seven and from one 

 to six members respectively. No second member of 

 the third series was found. In the series terms listed 

 below, the Fowler notation is used with the modifica- 

 tion that P is used instead of p for the common head 

 of the new triplet series. This change was suggested 

 to me by Prof. R. T. Birge. The wave numbers of 

 the head oPj^g of the series are 109833, 109674, and 

 109607. Only the shortest wave-length of each 

 member is noted, but the others were observed and 

 may be readily calculated from the data given here ; 

 0P3-1S, 2S, . . . 7S are X's 1302-27, 1039-26, 



M 2 



