f T, . T ^-r, ^^,T^C, » 



MIRAGE OR ' FALSE PONDS. 99 



ponds.' Even the experienced traveller is often 

 deceived by these upon the arid plains, where 

 a disappointment is most severely felt. The 

 thirsty wayfarer, after jogging for hours under 

 a burning sky, at length espies a pond — yes, 

 it must be water — it looks too natural for him 

 to be mistaken. He quickens liis pace, en- 

 joying m anticipation the pleasure of a re- 

 fresliing draught : but lo ! as he approaches, 

 it recedes or entirely disappears ; and when 

 upon its apparent site, he is ready to doubt his 

 own vision — he finds but a parched plain un- 

 der his feet It is not mitil he has been thus 

 a dozen times deceived, that he is willing to 

 relinquish the pursuit : and then, perhaps, 

 when he really does see a pond, he will pass 



it unexamined, for fear of another disappoint- 

 ment. 



The philosophy of these ' false ponds' seems 

 generally not well understood. They have 

 Usually been attributed to refraction, by Avhich 

 a section of the bordering sky would appear 

 below the horizon : but tliere can be no doubt 

 that they are the effect of reflection, upon a 

 gas emanating perhaps from the sun-scorched 

 earth and vegetable matter. Or it may be 

 that a surcharge of carbonic acid, precipitated 

 upon the flats and sinks of those plains, by the 

 action of the sun, produces the effect At 

 least, it appears of sufficient densit}', when 

 viewed very obUquely, to reflect the objects 

 beyond : and thus the opposite sky being re- 

 flected in the porid of gas, gives the appear- 

 ance of water. As a proof that it is the effect 



