ii6 



NATURE 



[December 19, 1918 



,1,, abrasion "I its foundations which do not enter 

 into the physics of ice-masses oi smaller dimensions. 

 Here the static pressure on the lower zones "I the ice 

 may reach 1 ton per sq. in. At the same time, the 

 temperature maj be so increased b\ ground heat as 

 to be much higher than that prevailing above, As a 

 consequence, when the ice-formation is very thick a 

 i plastic ba >e must !»• admitted. 



The outflow of the inland ice i- principally deflected 

 ;u the coastal margin into depressed areas outlining 

 the heads of gulfs and bays. In such localities the 

 rate ol mo\ emenl and the volume of ice enti ring the 

 si a are. both great so gn at, indeed, thai 1 xtensive 

 floating "glacier tongues" are .1 Feature _ ol such 

 situations, ofti n to fifty miles from 



the shore. 



Along othei stretches of the coasl less well placed 



For receiving tributions from the int. rim- of the 



continent the outflow is so much less that the destruc- 

 tive influences .it work on reaching the sea easily 

 maintain its boundaries at approximately the true 

 coast-line. 



As exceptions in this latter prevailing condition, 

 however, there are known already two notable locali- 

 ties where thi general overflow from the land main- 

 tains itself as an immensely thick floating structure 

 extending Far out over the sea -a veritable oceanic 

 ice-cap. To this type of formation we apply Prof. 

 Nordenskjold's term ■'shelf-ice." The formations 

 referred to are the Great Ross Barrier at the head of 

 the Ross Sea, and the Shackleton Shelf off the coast 

 of Queen Mary I .and. 



The former occupies what is really the head of the 

 Ross Sea— a somewhat triangular area. From apes 

 to base it measures five hundred miles, with a base- 

 length of aboul four hundred miles. This great raft 

 of ice presses forward to the open sea at the rate of 

 a few hundred yards per annum. The available 

 figures, quoted by David and Priestly, show that, at 

 the present rate of advance, the ice now appearing at 

 the sea-face must have left the inner extremity of the 

 floating sheet at some lime during the seventh cen- 

 tury. A survey of the ice-cliff forming the sea-face 

 indicates by its changing height that the Ross Barrier 

 is of varying thickness. This has been explained by 

 the presence, in localities where it is thickest, of the 

 remnants of the massive-ice contribution received 

 during its course from certain of the large tributary 

 glaciers. The ice from these glaciers, in fact, con- 

 stitutes a strong framework which stiffens and con- 

 tains the more crumbling structure derived from the 

 eonsolid.ation of the annual snowfall. 



To a great extent this must certainly be so; but 

 tin- influence of a varying snowfall, and the effect of 

 violent periodic winds— a feature of the region in 

 sweeping the loose mhhv from certain areas and de- 

 positing it in other favoured localities, niu^t be 

 oned with. The snowfall is lighter on the eastern 

 side than on the wast. Furthermore, the snow tends 

 i.i accumulate on the western side owing to the fact 

 that tin- winds regularlv blow from the quarter south 

 to east, and not from the west. 



In the case of the Shackleton Shelf, ibis is the 

 more remarkable because it maintains itself as a 

 pontoon stretching into the open sea, even across the 

 drift of the prevailing ocean current. 



The deluge of ice, after descending to tin- sea, 

 presses northwards as an integral whole, at first 

 touching bottom at intervals, then forcing its wa\ past 

 several islands, and eventually reaching an extremi 

 distance of 180 miles from the land before it is mas- 

 tered bv the swell and currents of the Southern Ocean. 

 Tt is somewhat triangular in form, with the apex out 

 tn sea. The base against the land, though not com- 



3STO. 2564, VOL. I02] 



pletcl charted, extends in all probability lor .1 dis- 



,.111.' oi about two hundred miles. 



I in main body of the shelf-ice advances rather 

 slowly, bul the D.-nman Glacier, which 1 onti -ibuti s to 

 it, has a much mi-rre rapid movement, verj well illus- 

 trated b) the fail of iis ploughing through tin othi t 

 -ii. If-ici ■ ith -11. h lone that a shatter-zone somi mill s 

 developi d. 



The wall oi the shelf-ice on the west sidi offers 



llenl example for study, as it is a section 

 from the point of its departure from the land to iis 

 crumbling apex. In the ease of the Kuss Barrier, the 

 ■ v .1 section across the direction of movement. 

 \t tin land ' nd the Shackleton Shelf, from the sur- 

 face down, is hard glacier-ice breaking with a charac- 

 teristic fracture. A few- miles Farther out, awa 

 the influence of the winds desci nding from thi land 

 lop . 1 in. mill commences to make its ap- 



|i 11. imi. over tin- original ice I. hi lation. \- one 



along the face awaj from the land ibis capping 



is observed to increase steadih in thickness. The 

 overburden of n£v£ is arranged in regular hands, each 

 of which corresponds with a single year's addition. 

 This bring so, it is possible to make some sort of 

 estimate of the .age of the Formation. 



The weigh! of these additions depresses the top 

 of the miginal ice below the surface of the water, 

 ["hough there is a regular annual addition above, it 

 must not he imagined that the total thickness "I thi 

 pontoon is correspondingly increased; for tin si, lo- 

 tion of the lower surface bv the sea has also to he 

 reckoned with. Very often, however, in the nivi 

 sections of glacier-tongues the cliff-face above the 

 witter is observed to stand higher than in the wholly 

 ice zone .11 the land end. This is to be expected on 

 account of the lighter nature of the ik'tv ice added, 

 there being ii larger proportion of air sealed up in it. 



The observed height above sea-level of Antarctic 

 shelf-ice so far recorded ranges from about jo ft. to 

 mine than 200 ft. A common figure is from on It. to 

 ijn ft., suggesting a total thickness of 6ob ft. to 

 1000 ft. 



Although the height of the cliff-face presented by 

 shelf-ice gives some idea of its total thickness, a really 

 accurate method of determination is badh needed. 

 I In Australasian Fxpedition hit upon a method which 

 ::n . - positive results, in some cases a' least. This 

 consists in taking serial temperatures of the sea-water 



in depth near the fare of the shelf-ice. As there is 

 alwavs a current flowing beneath the i. • . thi 



of it is likelv to he marked bv a sudden slight change 

 in the water temperature, easily observed when the 

 ations are plotted as a graph. 



UNIVERSITY, AND EDUCATIONAL 

 INTELLIGENCER. 



( imbridge. 'The titular degree of M.A., honoris 

 causa, hits been conferred upon Mr. Frederic William 

 Hat tiler, of Norwich, in recognition of his researches 



in logy, especially the geologj of the Eastern 



Counties. Mr. Ilarmer is the father of Dr. S I 

 llatnier. Keeper of the Department of Zoology, 

 British Museum (Natural History). 



London. At University College arrangements have 

 now been completed in the facult) of engineering to 

 enable students whose courses have been interrupted 

 bv war service, or those who were unable to begin 

 ih.ii engineering studies last October owing i<> war 

 conditions, to resume or begin their studii s bj i nt< r- 

 ing next term, January i ;, toi<>. For both 1I.1-' s of 

 students additional work will be provided durin 

 ,,f the Easter and Long Vacations, so as to enable 



