ON ITS EXTEBIOR. VOLCANOES. 313 



indicate porphyritic schist. All the blocks have a 

 yellowish grey crust from weathering. As the line of 

 rocky fragments (the Spanish-speaking natives call it 

 los derrumbamientos, la reventazon) extends from the 

 Eio del Molino, not far from the hacienda of Pintae, up 

 to the small pumice-surrounded crater lakes, the impres- 

 sion which naturally presented itself was, that the hol- 

 lows now filled with water are the orifices through which 

 those fragments came to the surface. A few years before 

 my arrival in the country, without any preceding sensible 

 agitation of the ground, the rocky fragments were in a 

 state of motion down the declivity for weeks, and some 

 houses at Pintac were overthrown by their impetus and 

 pressure. They are still without any trace of vegetation ; 

 which is beginning to appear, though sparingly, on the 

 doubtless older and more weathered blocks on the high 

 plain of Antisana. 



What name ought we to give to the particular mani- 

 festation of volcanic activity, whose effects I have been 

 describing ? ( 448 ) Have we here to do with lava-streams ? 

 or only with semiscorified and glowing masses, ejected 

 disconnectedly but in close succession, as has been seen 

 to take place in very recent times on Cotopaxi ? May 

 it even be possible that the dykes of stones of Yana 

 Volcan and Ansango may have been fragmentary masses, 

 which, being loosely heaped up, and therefore imper- 

 fectly supported, in the interior of the volcano, may 

 have been displaced by earthquakes, and then by their 

 fall and shock have occasioned small local agitations, 

 and thus have been ejected without any renewal of 

 higher temperature in the volcano? Or are none of 

 the three very different manifestations of volcanic ac- 



