ON ITS EXTEBIOR. VOLCANOES. 319 



scoriae, molten only at their edges, sometimes angular 

 and sometimes roundish, of six or eight feet diameter, 

 rarely scaly, like those on Antisana, have all been 

 thrown up to great heights from the summit-crater, and, 

 falling down on the declivity, have had their move- 

 ment accelerated by the rush of melted snow water ; 

 or whether, without having been thrown up into the 

 air, they have been expelled from lateral fissures of the 

 volcano, as the word reventazon would indicate, remains 

 uncertain. Returning soon from Suniguaicu and the 

 Quebrada del Mestizo we examined the long and broad 

 ridge, which, stretching from KW. to S.E., connects 

 Cotopaxi with the Nevado de Quelendana. Here the 

 blocks arranged in line are wanting, and the whole 

 appears a dyke-like elevation, on which the small conical 

 Mount el Morro rises, and nearer to Quelendana (which 

 has the shape of a horse-shoe,) there are several marshes 

 and two small lakes, the Lagunas de Yauricocha and de 

 Verdecocha. The rock of el Morro and of the whole 

 linear volcanic elevation was greenish-grey porphyritic 

 schist, in beds or strata eight inches thick, dipping 

 very regularly towards the east at an angle of 60. 

 Of proper currents of lava, there was nowhere any 

 trace. ( 454 ) 



There is an analogy between what takes place in the 

 Island of Lipari, rich in pumice, where on the north of 

 Caneto a lava-stream of pumice and obsidian descends 

 from the well-preserved extinct crater of the Monte di 

 Campo Bianco towards the sea, in which it is remarka- 

 ble that the fibres of the pumice are parallel to the di- 

 rection of the stream ( 455 ), and the local relations, which 

 were carefully examined by me, of the extensive pumice- 



