14 LIGHT SCIENCE FOR LEISURE HOURS. 



in modern times. He refers, doubtless, to the Peruvian 

 and Colombian Andes, and not to the Chilian. In the 

 latter portion of the range there must be a continual 

 increase of height, since each earthquake in Chili has 

 produced a perceptible recession of the sea. Darwin, 

 indeed, relates that near Valparaiso he saw beds of 

 sea-shells belonging to recent species at a height of 

 about a quarter of a mile abovo the present sea-level ; 

 and he concluded that the land had been raised to this 

 height by a series of such small elevations as were ob- 

 served to have 'taken place during the earthquakes of 

 1822, 1835, and 1837. That a contrary process should 

 be going on in Peru, confirms the idea that a sort of 

 undulatory or balancing motion is taking place one 

 long stretch of the Cordilleras rising while another is 

 sinking. A tradition prevails among the Indians of 

 Lican that the mountain called L' Altar, or Cassac 

 Urcu which means " the chief" was once the highest 

 of the sub-equatorial Andes, being higher even than 

 Chimborazo ; but, adds the tradition, in the reign of 

 Quainia Abomatha, before the discovery of America, a 

 prodigious eruption took place which lasted no less 

 than eight years, and brought down the summit of the 

 mountain. M. Boussingault states that the fragments 

 of trachyte which once formed the summit of this cele- 

 brated mountain are now spread over the plain. At 

 present Cotopaxi is the loftiest volcano of the Cordil- 

 leras, its height being no less than 18,858 feet. 'No 



