AERIAL SPECTRES BY REFLECTION. 213 



beyond the horizon, and some leagues beyond the limit of 

 direct vision. I was so struck with the peculiarity of the 

 circumstance, that I mentioned it to the officer of the 

 watch, stating my full conviction that the Fame was then 

 cruising in the neighbouring inlet." 



Several curious effects of the mirage were observed by 

 Baron Humboldt during his travels in South America. 

 When he was residing at Cumana, he frequently saw the 

 islands of Picuita and Boracha suspended in the air, and 

 sometimes with an inverted image. On one occasion he 

 observed small fishing-boats swimming in the air, during 

 more than three or four minutes, above the well-defined 

 horizon of the sea, and when they were viewed through a 

 telescope, one of the boats had an inverted image 

 accompanying it in its movements. This distinguished 

 traveller observed similar phenomena in the barren 

 steppes of the Caraccas, and on the borders of the Orinoco, 

 where the river is surrounded by sandy plains. Little 

 hills and chains of hills appeared suspended in the air, 

 when seen from the steppes, at three or four leagues 

 distance. Palm trees standing single in the Llanos 

 appeared to be cut off at bottom, as if a stratum of air 

 separated them from the ground ; and, as in the African 

 desert, plains destitute of vegetation appeared to be rivers 

 or lakes. At the Mesa de Pavona M. Humboldt and 

 M. Bonpland saw cows suspended in the air at the distance 

 of 1000 toises, and having their feet elevated 3' 20" above 

 the soil. In this case the images were erect, but the 

 travellers learned from good authority that inverted 

 images of horses had been seen suspended in the air near 

 Calabozo. 



In all these cases of aerial spectres the images were 

 directly above the real object; but a curious case was 

 observed by MM. Jurine and Soret on the 17th Sep- 

 tember, 1818, where the image of the vessel was on one 



