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seven or eight metres. The surrounding rocks, 

 which remind us of the cave of Fingal, at 

 Staffa, in the Hebrides ; the contrasts of vege- 

 tation, the wild appearance, and the solitude of 

 the place, render this small cascade extremely 

 picturesque. On both sides of the ravine the 

 basaltic columns rise to more than thirty metres 

 in height, and on them grow tufts of cactus and 

 yucca filamentosa. The prisms have generally 

 five or six sides, and are sometimes as much as 

 twelve decimetres in breadth ; several present 

 very regular articulations. Each column has 

 a cylindrical nucleus, of a denser mass than the 

 surrounding parts ; these nuclei are as it were 

 enchased in the prisms, which in their horizontal 

 fracture offer very remarkable convexities. This 

 structure, which is also found in the basalts of 

 Fairhead, I have shown in the foreground of the 

 drawing toward the left. 



The greater part of the columns of Regla 

 are perpendicular ; though some very near the 

 cascade, have forty-five degrees of inclination 

 toward the east ; and farther on there are others 

 horizontal. Each group, at the time of its for- 

 mation, appears to have followed particular 

 attractions. The mass of these basalts is very 

 homogeneous. Mr. Bonpland remarked in them 

 nuclei of olivine or granuliform peridot, sur- 

 rounded with mesotype-zeolite. The prisms, 

 and this fact deserves the attention of geologists, 



