AN ATMOSPHERIC DELUSION. 143 



and returning into the feverish activity of existence. But soon, the 

 atmospheric forces which had raised them beginning to fail, we saw 

 these sand-spouts fall away one after another, and form on the surface 

 of the Desert a number of moving hillocks similar to those from 

 which we had just emerged." 



The poet, invoking the judgment of Heaven on the traitor, would 

 fain doom him to the misery of cherishing hopes that shall never be 

 realized. " May he," cries the minstrel 



" May he, at last, with lips of flame, 

 On the parched desert thirsting die, 

 While lakes that shone in mockery nigh 

 Are fading oft, untouched, untasted."* 



The image here is borrowed from that most singular phenomenon 

 of the Desert, the Mirage ; an atmospheric illusion due to the refrac- 

 tion of the sun's rays upon the sand, and the intense expansion of the 

 lower strata of the air, in other words, it arises from the total 

 reflection of the rays of light from the lower surface of a stratum of 

 air. " This occurs when, from any cause, such a stratum of air pos- 

 sesses a higher refractive power than the one immediately below it. 

 Such a condition of the atmosphere causes remote objects to be seen 

 as if reflected in a mirror, or to appear as if suspended in the air. 

 When the effect is confined to apparent elevation, the English sailors 

 call it looming ; when inverted images are formed, the Italians give 

 it the name of Fata Morgana.. The Arabs call it Serab, or Suhrab, 

 the ' Water of the Desert ; ' and the Hindus, Tchittram, or ' the 

 Picture.' " 



The effects of the illusion are extraordinary, but undoubtedly 

 they are heightened by the imagination of observers, generally over- 

 excited by fatigue, by privations, or sometimes by fever. These 

 causes contribute to vary the nature of the phenomenon as seen by 

 different eyes. Thus some gaze enraptured on verdurous islands 

 bright as Armida's enchanted garden, with feathery palms and bloom- 



* Moore, " Lalla Eookh "The Fire-Worshippers. 



