340 



AEKIAL REFLICTTON. 



rent and colourless. Will it be said, that the gold is simply 

 —yet this af. divided in this glass ? If fragments of it be heated in a retort, 

 c™roiour- """"^ consequently far from any dephlogisticating vapour, they 

 ed when heat- will acquire a superb purple tint, without lossing any thing of 

 t^^eir transparency. Can this result be called a metallic re- 

 duction ? The purple of enamels, and of painting on porce- 

 lain, frquently disappears, and afterward reappears with the 

 greatest facility. Do we here recognize a metal that never 

 S'dnotunder-'^^'''''^''" fr"'" metallic simphcity in its different states? gold, 

 stood. dissolved in glass, does, or does not, produce colours. This is a 



phenomenon in its history of which we know not the cau^e. 

 Let us then honestly confess with Macquer, " this purple state 

 " of gold is not yet well understood." 



VIII. 



Accovnt of an Appearance of Brighton Cliff seen in the Air 

 hy Reflection. In a Letter from Dr. Buchan. 



To Mr. NICHOLSON. 

 Dear Sir, 



l»troduction. vJ'N reverting to some notes made at the time I found the 

 subsequent account of the appearance, which I mentioned to 

 you in conversation yesterday, and which you seemed to think 

 \yorthy of recording. Perhaps you, or some of your corres- 

 pondents, may favour the readers of the Philosophical Journal 

 with an explanation of the optical principles on which the phe- 

 nomenon depends. 

 The cliff was Walking on the cliff, about a mile to the eastward of Bri^ht- 

 H-'e" perfectly helmstone, on the morning of the 28th of November 1804-, 

 repie ented by while watching the rising of the sun, I turned my eyes directly 

 reflecti^ii,^ towards the sea, just as the solar disk emerged from the sur- 

 face of the water, and saw the face of the cliff on which I was 

 standing, represented precisely opposite to me at some distance 

 on the ocean. Calling the attention of my companion to this 

 appearance, we soon also discerned our own figures standing 

 on the summit of the apparent opposite cliff, as well as the re- 

 presentation of a windmill near at hand. The reflected 



images 



