HORN EXPEDITION — PHYSICAL GEOGRAPHY. 21 



Lake Amaclcus itself was discovered and named by Mr. Ernest Giles in 1872, 

 when it pi'uved an insuperable obstacle to him in his westward course towards 

 Western Australia. In 1873 it was crossed by Mr. Gosse at a narrow neck near 

 its eastern extremity ; but in the next year Mr. Giles was again forced to retrace 

 his steps, the bed of the lake, where examined by him, being found to be so boggy 

 as to be impassable. In 1889 Mr. Tietkens examined the western portion of the 

 lake, and was consequently able to define approximately its true outline, whicli 

 had previously been extremely hypothetical. llis examination of the lake 

 resulted in the shortening of its length, as shown on the maps up to that time, 

 by more than 100 miles. 



Its extreme western portion, wiiich was previously supposed to be situated 

 about 128° 10' in Western Australia, and to be about twenty to thirty miles wide, 

 is now known to be situated in South Australia, about 130° 18', and to be only 

 from two to three miles wide. 



According to Mr. Tietkens, its extreme length is about ninety-two miles, 

 while its width varies from two to fifteen miles, the maximum width of fifteen 

 miles occurring about the 131st meridian. At tlie narrow neck, however, where 

 we crossed, it is not more than three-quarters of a mile wide. 



The area of the lake is approximately 700 sijuare miles, and its altitude above 

 sea level must be more than 1000 feet. 



One set of calculations of its elevation were based on Mr. Winnecke's figures 

 for the altitudes of the camps at Bagot Creek and Reedy Hole, and on the 

 differences between the barometrical readings at those places and at Lake 

 Amadeus ; while another set were based on the barometrical readings given by 

 Mr. Tietkens in his Journal, etc. 



As far as known, Lake Amadeus receives the drainage of a few small creeks 

 only, as no rivers of any importance have up to the present time been discovered 

 within the area of its basin. The view of the lake gained from the neighbouring 

 sandhills is a very remarkable one. Stretching away to the east and west as far 

 as the eye could discern was a dazzling, white, flat expanse, on whose surface no 

 water could be seen, but in its place a coating of a white saline material, which on 

 analysis proved to be composed almost entirely of coumion salt, with a small 

 amount of sulphate of lime (gypsum). On closer examination the saline crust was 

 found not to exceed a quarter to half an inch in thickness, under wjiich was a red 

 argillaceous sand passing down into similar material of a grey colour. The surface 

 of the lake was found to be tolerably firm, the horses only sinking to the depth of 



