156 THE CHEMISTRY OF CREATION. 



combustion, of which the principal product is 

 sulphuric acid. But this combustion is ren- 

 dered visible to the eye in a striking degree. 

 On holding a lighted cigar near the stream of 

 gas from the volcano, although all other tests 

 failed to indicate the presence of sulphuretted 

 hydrogen in it, it was by so doing instantly ren- 

 dered sensible. A dense cloud of vapour in- 

 stantaneously emanated from the burning body, 

 and diffused itself, like the smoke which in 

 Arabian fable poured from the fisherman's bottle 

 until it assumed the form and magnitude of a 

 geni, far over the ravine and the plain of the 

 fumeroles. At almost all the hot springs, this 

 remarkable phenomenon could be produced. 

 Even the light vapour which rises from the clear 

 bluish-green water of the basin of the large 

 crater was converted, on the approximation of 

 a burning body, into a dense cloud of vapour, 

 which would envelope the whole mirror of the 

 water, spreading in all directions, and almost 

 leading the astonished traveller to anticipate 

 the appearance of some giant form in its 

 wreathing folds. By the constant passage of 

 the volcanic gases through the palagonite, a 

 number of chemical phenomena are continually 

 proceeding; and the changes thus produced are 

 manifest on the surface in saline incrustations 

 and mineral productions of various kinds. 



