Fata Morgana. 49 



ship. None of these people had ever seen so large a man- 

 of-war, and they all therefore regarded the ship with great 

 curiosity. The ship's band greatly delighted them, but the 

 signal-gun at sunset seemed to terrify them and to hasten 

 their departure. 



In the evening we felt from time to time some warm 

 blasts of wind from the east, and enjoyed for nearly an hour 

 the delightful spectacle of a " Fata Morgana." This pheno- 

 menon, as is well known, arises from two currents of air of 

 a different density, separated by a distinctly-formed plane, 

 generally produced when the temperature of the two cur- 

 rents happens to vary. When, for instance, as is frequently 

 the case at sea, a considerably warmer current of air comes 

 suddenly in contact with a colder current having a lower po- 

 sition, the plane of separation of the former becomes con- 

 densed, and forms a mirror for all those objects which are 

 in the lower current, so that their image is inversely re- 

 flected. As this surface of separation is not level through- 

 out, various contractions and distortions result, which impart 

 to the whole a singular appearance. On land, as for in- 

 stance in the deserts of Africa, where the warmer current 

 of air is on the surface of the ground, the aerial mirror is 

 formed beneath the eye of the observer, by which the same 

 phenomenon is produced that results from the reflection of 

 objects on the surface of the water. 



In the present case the temperature of the atmosphere was 

 about ten degrees higher than that of the sea's surface at the 



E 



