SIX MONTHS IN MEXICO. 207 



down, immense masses of broken rocks, some 

 of them of many hundred tons weight; — 

 these, floating like corks on the melted lava, 

 had met with some impediment in their way, 

 and remained piled upon each other by the 

 impetuous burning stream, in the most extra- 

 ordinary manner, leaving to distant ages these 

 striking proofs of the horrid combustion of 

 internal subterraneous fires, by which the 

 higher mountain districts have been formed. 



One of our guides returned to say they 

 had found the cave, and to accompany us to 

 it : we commenced our short journey over the 

 scene of desolation I have been attempting to 

 describe, but we moved forward with diffi- 

 culty, as, independent of the steep and sharp 

 precipices we had to cross, there was much 

 danger of falling into the deep fissures and 

 rents formed by the cooling and shrinking of 

 the melted matter which occupied the whole 

 valley. 



