EXTINCT \OLCAXOES OF XURTiiHAST XHW MEXICO 



363 





HORSESHOE MOUNTAIN, A VOLCANIC CINDER CONE OF RECENT ORIGIN. NEAR 



CAPULIN MOUNTAIN. 



in turn attracted wolves, wild cats, and 

 other savage animals, as well as savage 

 men, so that good hunting was afforded 

 as well as safe habitation. Also, the 

 cavernous "mal pais" has the power of 

 this semi-arid region, and springs of 

 pure water often occur in or near it, 

 although in other kinds of rock in the 

 same region the springs may be very 

 poor or wholly wanting. 



BLISTER CONES 



Blister cone is a name applied to cer- 

 tain elevated parts of the surface of 

 mal pais. They are often conical, 

 globular, or elliptical, and consist of 

 irregularly shaped blocks of lava. In 

 the more perfect ones these blocks are 

 arranged in symmetrical order as if 

 fitted together by design. Obviously, 

 they were formed at a time when a 

 solid crust had formed at the surface 

 of the lava that was still viscous below, 

 and shortly before the whole mass 

 ceased to move. Thus the rigid crust 

 buckled and broke as the viscous mass 

 beneath continued to move. The early 

 blisters were destroyed entirely; later 

 ones, broken and warped out of shape, 

 appear now as heaps of blocks without 

 symmetry of form ; still later ones ap- 

 pear in such perfect symmetry as the 



one illustrated ; and the last to form 

 may appear as oval mounds of slight 

 elevation. Blisters may be found show- 

 ing every stage from the first slight 

 buckling of the crust to unsightly heaps 

 of angular blocks. 



In the more perfect blisters the form 

 and structure indicate that the blocks 

 are parts of a once continuous crust 

 or sheet of lava, although they are now 

 separated by considerable distances. 

 In many places the cavities are large 

 enough for a man to crawl through. 

 Into the base of one of these blisters 

 near Capulin, a young man who accom- 

 panied the writer made his way on 

 hands and knees, and after a tortuous 

 passage among the blocks he emerged 

 from the top, 20 feet above the point 

 where he had entered. This, however, 

 is an operation that few would care 

 to repeat, for the knifc-likc edges of the 

 lava cut one's clothing and lacerate 

 one's hands. But the more serious ob- 

 jection arises from the fact that rattle- 

 snakes which infest this region regard 

 these cavities as their own private do- 

 main. The dark-colored lava is 

 warmed by the rays of the sun, and 

 these venomous "sons of Satan," as 

 they are often called, seem to find con- 

 ditions here quite to their liking. Their 



