sou HOT SPEINGS. 705 



monotonous dreary valley. Scattered over the top are ten or twelve liot- 

 spring pools, almost circular in outline, varying from 6 to 60 feet in diame- 

 ter, remnants of a much greater activity of thermal waters, and known as 

 the Sou Hot Springs. ' ' 



On Plate XX is given a general view of this group of hot springs, show- 

 ing their position on the border of the valley with the Osobb Desert, stretch- 

 ing far away to the southward. The ground is covered with a loose alkaline 

 soil, over which is a scanty vegetable growth, somewhat richer in the im- 

 mediate neighborhood of the springs. In the illustration, only a few of the 

 larger and more elevated pools are shown, the others either lying at a lower 

 level or hidden by the inequalities of the surface. Around each spring 

 there has been built up a secondary mound or rim of calcareous tufa, which 

 in some instances has contracted as it formed, producing a perfect dome 

 over the hot spring, with a vent of 2 or 3 feet in diameter. The tempera- 

 ture of the hottest of those observed varied from 160° to 185°, although 

 several of the largest springs have an agreeable temperature for bathing; 

 indeed, a remarkable feature in connection with these springs is the very 

 great variation of temperature within short distances. The waters are 

 charged with chlorides and sulphates of the alkalies, together with small 

 amounts of other salts, in which, however, the sulphate of soda largely 

 predominates. 



.The residue obtained from the evaporation of the water from one of 

 the largest hot springs was subjected to qualitative analysis by Prof 0. D. 

 Allen, of the Sheffield Scientific School, who reported the following ingre- 

 dients: chlorine, carbonic acid, sulphuric acid, and soda, with traces of iron, 

 lime, magnesia, and potassa. 



A large amount of the alkaline efflorescence mixed with the fine, almost 

 ^ impalpable, surface-soil surrounding the same spring was collected from 

 among the grass-roots, and submitted to Prof 0. D. Allen for the purposes 

 of chemical examination. 



Upon being treated with water, it left a very considerable residue, 

 which consisted chiefly of sulpho.te of lime, with small amounts of silica, 

 iron, magnesia, and a trace of phosphoric acid. 



45 D G 



