20 HORN EXPEDITION — PHYSICAL GEOGRAPHY. 



Tlie western boundary of the Lake Eyre Basin is formed by the Cretaceous 

 plains Hanking on the east tlie Everard Range, in which the Neales River takes 

 its rise, by the eastern extremity of the Musgrave Range, from which the Alberga. 

 heads, and by the western extremities of the George Gill and Gardiner Ranges, 

 where some of the large tributaries of the Finke have their sources. The northern 

 boundary is formed by the McDoiniell and Hart Ranges. The north-eastern and 

 the eastern are formed by the Selwyn, McKinlay, and the Great Dividing Ranges, 

 in which the sources of the Mulligan, Diamentina, and Barcoo (Cooper's Creek) 

 are situated. Lastly, the southern boundary is for the most part formed by the 

 northern slope of the Flinders Range, from which short narrow creeks flow north- 

 wards to Lake Eyre. 



Form, Area, etc. — The general form of the basin is roughly quadrilateral, 

 with one angle situated on the northern slope of Flinders Range, to the south of 

 Lake Eyre south. Another of the angles coincides with the western extremity of 

 the McDonnell Ranges about Mount Ziel. A third lies near the head of the 

 Mulligan and the last is situated about the source of the Barcoo River. The 

 total area of the basin cannot be less than 500,000 square miles, the greatest 

 breadth, lying along the 24th parallel, is about 900 miles, and the greatest 

 length, occurring about the 137th meridian of E. longitude, is about 750 miles. 



Lake Eyre itself, including Lake Eyre south, lies within the 137th and the 

 138th meridians of E. longitude and between 27° 50' and 29° 29' S. latitude, and 

 occupies an area of about 5000 square miles. It is situated almost at the very 

 southern extremity of the basin, the south edge of Lake Eyre south being only a 

 few miles north of the northern extremity of Flinders Range. The margin of 

 Lake Eyre has been calculated to be thirty-nine feet below sea level. 



Lake Amadeus. 



The Lake Amadeus Basin is not well known, but it appears to be of small 

 extent as compared with that of Lake Eyre. It comprises in all probability an 

 area of between 20,000 and 30,000 square miles. The northern boundary of the 

 basin extends probably from the western end of George Gill Range to Watson 

 Range, and thence along the north of the 24th parallel to about the Western 

 Australian border. The southern limit of the basin lies possibly along the 

 Rawlinsou and Petermann Ranges, while its eastern and western boundaries are 

 apparently unknown. 



