Volume 14 Australasia - dana ward's homepage

26 AUSTRALASIA.general backward movement of the oceanic waters malces itself felt. It has anestimated mean breadth of three hiindred miles ; but it follows a somewhatirregular course, and in many places merges in lateral backwaters.The Indian Ocean has also its counter equatorial stream skirting the north sideof the current which sets towards the west. Students of historical migrationsattach the greatest importance to those parallel currents flowing in ojDposite directions,and thus facilitatiug the movement of peojjles from continent to continent.Drift Ice— Icebergs and Floes.Round about the Antarctic ice-cap the approach to the islands and mainland isobstructed by continuous streams of drift ice and floes, which are constantly driftingFig. 9. Ice Field traced by Ditmont D'Ueville.Scale 1 : 1,330,000.u,0.:M,>about, in one place grouped together in the form of gulfs or marine inlets, inanother disposed like projecting headlands, elsewhere developing long narrowpassages into which navigators cannot venture to penetrate without extreme caution.Ranging in height from 10 to 14 feet, but here and there interspersed withirregular groups or " bunches," resembling erratic boulders, these masses no longerpresent an insurmountable obstacle to mariners provided with the powerful appliancesof modern mechanics, and with vessels specially constructed to resist theimpact or pressure of floating ice.Beyond these shifting barriers stretch comparatively open spaces which areoccupied only by great icebergs, either isolated or accompanied by a cortege oflesser blocks. Explorers who have penetrated into these Antarctic seas about thepolar circle, or even bej'ond 70° south latitude, have observed that these icebergs