246 EXTR^ORDIN^Rr EFFECT 



vation, I was fatisfied that it was a real image of the Caflle. 

 Upon this I gave the telefcope to a perfon prefent, who, upon 

 attentive examination, faw alfo a very clear image of the Caflle, 

 exadlly as I had defcribed it. He continued to obferve it for 

 about twenty minutes, during which time the appearance re- 

 mained precifely the fame \ but rain coming on, we were pre- 

 vented from making any further obfervations. Between us 

 and the land, from which the hill rifes, there was about fix 

 miles of fea, and from thence to the top of the hill about the 

 fame diflance, and we were about feventy feet above the fur- 

 face of the water. 



The hill itfelf did not appear through the image, which, it 

 might have been expected to do. The image of the Caflle ap- 

 peared very flrong, and well defined ', and although the rays 

 from the hill behind it, mufl undoubtedly have come to the 

 eye, yet fo it was, that the ftrength of the image of the Caflle 

 fo far obfcured the back-ground, that it made no fenfible im- 

 preflion upon us. Our attention was of courfe principally di- 

 rected to the image of the Caflle ', but if the hill behind had 

 been at all vifible, it could not have efcaped our obfervation, as 

 we continued to look at it for a considerable time with a good 

 telefcope. 



A phenomenon of this kind I do not remember to have 

 feen defcribed; and it mufl have been a very extraordinary 

 flate of the air to have produced it. It is manifefl, that a ray 

 of light coming from the top of the hill, mufl have come to 

 the eye in a curve lying between the two curves defcribed by 

 the rays coming from the top and bottom of the Gafllej in or- 

 der to produce the efFed. 



Let AB (Plate VIII. Fig. 2.) reprefent the Caflle, EC the 

 Cliff (at Ramfgate), BTD the Hill, DC the Sea, E the place 

 of the fpeclator, T the top of the hill, Ay v E a ray of 

 light coming from the top of the Caflle to the fpe&ator, 



JUt xwEl 



