27 



stretcliing to the foot of tlie opposite cliff. (See pi. III., 

 fig. 2). 



The extent of the flood-waters is marked by the presence of 

 the "box" or "swamp gum-tree" (^Eucalyptus largiflorens) ; it 

 and the red gum-tree {Tl. rostratd) are the only species of the 

 genus inhabiting the alluvial tracts. The latter grows about 

 the permanent water ; whilst its congener prefers drier ground, 

 though it is evident that its seeds require longish immersion in 

 water to effect germination. E. largiflorens attains a maximum 

 height of about 100 feet where growing in spots annually 

 flooded ; but depauperated specimens may here and there be 

 seen considerably beyond the limits of the greatest flood on 

 record, which seems to demonstrate that at no distant date still 

 higher floods have occurred than we know of. This fact is so 

 well-known on the river that no permanent habitation of any 

 value is erected within the zone of the " box." 



Mr. Pollitzer has shown by table the fluctuations of the 

 water-level at Overland Corner during the last five years, from 

 which we gather the highest elevation above zero of the Over- 

 land Corner gauge, for each year, to be as follows : — 1879, 18 

 feet in December ; 1880, 18 feet in January ; 1881, 10 feet in 

 January ; 1882, 10 feet in November ; 1883, 9 feet in January. 

 The river is at a minimum level varying from March to May, 

 begins to rise with the winter rains in June, and has the largest 

 volume by the melting of snow in the summer months of 

 December and January. The volume of water is largely 

 dependent on these two sources, and an intermittent supply is 

 furnished by the Darling. The tropical rainfall, which comes 

 usually in February and March, and partially so in December, 

 sets the Darling in flood. The flood-waters of the Darling 

 reach the Murray after an interval of four weeks, the average 

 velocity being about 50 miles per day. The volume of water in 

 the Darling is at other times insignificant. If the tropical 

 rains of December be heavy, and should the winter at the 

 sources of the Murray be protracted, then the united flood- 

 waters of the two rivers deluge the whole country within the 

 gorge of the Lower Murray — these exceptionally high floods 

 occur only at long intervals of time. 



In the upper section of the river the flood-waters have a 

 great area over which to spread themselves, whilst within the 

 narrow gorge of the lower section the volume of water is com- 

 pressed, and in consequence the maximum heights of the flood 

 are here very much greater than they are in the upper section. 

 The highest flood-marks at Morgan are 36 feet above summer 

 water-level. 



The much-discussed question of how to improve the naviga- 

 bility of the Murray raises several subsidiary ones, the im- 



