PHILOSOPHICAL 

 TRANSACTIONS. 



XII. On double Images caused by atmospherical Refraction. By 

 William Hyde Wollaston, M. D. F. R. S. 



Read March 6, 1800. 



In some of the last volumes of the Philosophical Transactions, 

 there have been related many instances of strong atmospherical 

 refraction, by which, objects seen near the horizon have appeared 

 inverted, and the horizon itself either elevated or depressed. 



Mr. Huddart first took notice of a distinct image, inverted 

 beneath the object itself; and, in the Philosophical Transactions 

 for 1797, has described several such appearances, accompanied 

 with an optical explanation, wherein he shews, that the lowest 

 strata of the air were at the time endued with a weaker refrac- 

 tive power, than others at a small elevation. 



In the volume for 1799, Mr. Vince has given an instance 

 (Tab. I. Fig. 1.) where erect, as well as inverted images were 

 visible above, instead of beneath, the objects themselves ; and, 

 by tracing the progress of the rays of light, in a manner similar 

 to Mr. Huddart's, concludes that these phenomena arose 



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