A GBAND ii.I.cmi v\Tl< >v. 



were like rocks amidst this vast aea of vapours, and their 

 black tints were in line contrast with the whiteness of 

 the clouds, 



While they were climbing over the broken lavas of 

 the Ma. . they perceived a very curious optical phe- 

 nomenon, which lasted some minutes. They thought 

 .v on the east side small rockets thrown into the 

 air. Luminous points, about Beven or eight degrees 

 above the horizon, appeared first to move in a vertical 

 direction; but their motion was gradually changed into 

 a horizontal oscillation. Their fellow-travellers, their 

 guides • v< n, were astonished at this phenomenon, with- 

 out either Humboldt or Bonpland having made any 

 remark i^\ it to them. The travellers thought, at first 

 . that these luminous points, which floated in tho 

 air, indicate d some new eruption of the great volcano of 

 Lancerota; for they recollected that Bouguer and La 

 ( [amine, in scaling the volcano of Pichincha, were 

 witnesses of the eruption of Cotopaxi. But the illusion 

 1. and they found that the luminous points 

 were the images of a iveral stars magnified by the vapours. 

 These images remained motionless at intervals, they then 



emed to rise perpendicularly, descended sideways, and 

 returned to the point whence they had departed. This 

 motion lasted our or two seconds. Though thev had no 



act means of measuring the extent of the lateral shift- 

 ing they did not tic less distinctly observe the path of 

 the luminous poim. p did not appear double from an 

 »f mir . and left no trace of light behind. 

 Bringing, with the telescope of a small sextant, the stars 

 int<> contact with the lofty summit of a mountain in 



acerot . Bumboldt observed that the oscillation was 



