26 



AUSTRALASIA. 



general backward movement of the oceanic waters makes itself felt. It has an 

 estimated mean breadth of three hundred miles ; but it follows a somewhat 

 irregular course, and in many places merges in lateral backwaters. 



The Indian Ocean has also its counter equatorial stream skirting the north side 

 of the current which sets towards the west. Students of historical migrations 

 attach the greatest importance to these parallel currents flowing in opposite direc- 

 tions, and thus facilitating the movement of peoples from continent to continent. 



Drift Ice — Icebergs and Floes. 



Round about the Antarctic ice-cap the approach to the islands and mainland is 

 obstructed by continuous streams of drift ice and floes, which are constantly drifting 



Fig. 9. — Ice Field traced by Dumont D'Ubville. 



Scale 1 : 1,330,000. 



'a^^.^Àé^-" 



n Miles. 



about, in one place grouped together in the form of gulfs or marine inlets, in 

 another disposed like projecting headlands, elsewhere developing long narrow 

 passages into which navigators cannot venture to penetrate without extreme cau- 

 tion. Ranging in height from 10 to 14 feet, but here and there interspersed with 

 irregular groups or " bunches," resembling erratic boulders, these masses no longer 

 present an insurmountable obstacle to mariners provided with the powerful appli- 

 ances of modern mechanics, and with vessels specially constructed to resist the 

 impact or pressure of floating ice. 



Beyond these shifting barriers stretch comparatively open spaces which are 

 occupied only by great icebergs, either isolated or accompanied by a cortège of 

 lesser blocks. Explorers who have penetrated into these Antarctic seas about the 

 polar circle, or even beyond 70° south latitude, have observed that these icebergs 



