FORMATION OF THE GEYSERS. 157 



Perhaps one of the most interesting features 

 in the chemistry of this wonderful country is 

 the formation of its geysers. Professor Bunsen 

 explains the whole process in a beautifully 

 clear and simple manner. In the mutual re- 

 action of carbonic acid, sulphuretted hydrogen, 

 and heated water, and the palagonite, are com- 

 bined all the conditions required by nature 

 to convert, in the course of centuries, simple 

 boiling springs into geysers, whose clear, va- 

 poury, and foaming columns of water shall 

 burst from the summits of their self-created 

 craters, either continuously, or at periods of a 

 few minutes, hours, or days. The explanation 

 of this remarkable fact is as follows. The 

 water of these boiling springs contains a dis- 

 solved hydrate of silicia, which on its evaporation 

 is deposited around the mouth of the spring, on 

 the margin projecting beyond the level of the 

 water. Of course, in the basin of the spring, 

 and below its surface, no evaporation takes 

 place, and therefore no incrustation can occur. 

 Imagine, then, this process of incrustation 

 around the edge of the spring to continue for 

 years, the natural result would be that the 

 margin would become higher and higher, form- 

 ing a rocky tube of silicious matter. As the 

 margin rises, the water, of course, rises also, 

 being always a little below the latter. The 



