342 HOT-SPRINGS NEAR [PART II. 



The whole of this assemblage of springs covers 

 an extent of about two square miles. Many of 

 them are difficult and dangerous to approach, as 

 the whole area seems to be only a thin crust over 

 subterranean and volcanic caverns. The surface is 

 hard, white, and thin ; below this is a whitish 

 pumiceous and friable earth ; then a yellowish 

 earth, containing sulphate of iron or sulphur ; then 

 a chalcedony, perfect in some places, in others in 

 process of formation. The whole is about a foot 

 in thickness ; and below this is a grey, soft, and 

 generally hot mud. It often happens that this 

 crust breaks in, and dreadful scaldings not unfre- 

 quently occur. Near one of the springs beautiful 

 saucer-shaped aggregations of silex shoot up, not 

 unlike fungi on a moist surface. 



These hot-springs contain a great quantity of 

 silex, of which are formed the stalagmitic efflo- 

 rescences above mentioned, and which petrifies in a 

 very short time all substances that are thrown into 

 the water ; it also forms deposits of a chalcedony 

 that nearly resembles in colour and solidity the 

 flint of the English chalk. This generally indis- 

 soluble substance is here held in solution, not only 

 in consequence of the high temperature, but chiefly 

 by the alkaline elements of the water. In some 

 springs there are also found sulphate of iron and 

 sulphuretted hydrogen gas, which is perceived by 

 the smell. In the nature of their component parts, 

 in their periodical issue in jets, and in their high 



