j^o On the apparent Elevation 



treme edge of the moor. Theie trees alfo appeared to be 

 floating in the air, but they did not elevate themfelves above 

 the ground fo much as thofe I lirft obferved. As I advanced 

 further in the valley, my horizon did not any more change in 

 a perceptible manner; though my polition in regard to cer- 

 tain parts of the row of trees was confidcrably altered, which 

 produced feveral modifications of the phaenomenon. The 

 elevation of the trees above the horizontal furface incrcafed 

 the further I prr>ceeded, but gradually decreafed in thofe parts 

 from which I receded, and where it had firft begun, and at 

 length the whole difappeared when I afcended the oppolite 

 hill. 



This circum fiance of the phjenomenon led me to an 

 obfervation, from which I concluded that refraction had 

 no fliare in it. The maffes of the diftant trees which 

 raifed themfelves from the ground, were fituated between 

 parts of the foremoft row, which for a confiderable time did 

 not change their pofition ; and thefe unchanoed parts gave 

 me fixed points, bv which I was enabled to etiimate the ele- 

 vation of the objects ; and it was this eltimation which con- 

 du6i;ed me to a knowledge of the nature of the phrenomenon. 



The intervals where, in confequence of my progreflive 

 motion forwards, the heavens appeared under the moft di- 

 ftant trees, raifed themfelves more the lower mv ftation 

 became on the hill, and the further I advanced in the valley : 

 but the fummits of the floating trees were not elevated ; oa 

 the contrary, thev feemed fomewhat depreifed in comparifou 

 of the foremod trees. The mafl'es became fliortened below, 

 but at the top they remained on the fame level. I had fuffi- 

 cient opportunity to confirm this circumllance, as, by chan- 

 ging mv pofition in a vertical and horizontal direction, I faw 

 three different maifesfo totally difappear, that, in the interval 

 which thev before occupied in the row of trees, nothing 

 more was to be I'een but the |)ure heavens. On one of theie 

 maflcs difappeariug in this manner, when I retired back from 

 my pofition, there firft appeared towards the heavens fonie 

 brown. ipots, which were the higheft fummits of the trees ; 

 and the more I receded, the more it feemed as if a curtain 

 dropped down which concealed the part of the heavens 

 before feen. But with whatever attention I looked towards 

 the fpot where this curtain fell down, and where the fum- 

 mits of the trees at length difappeared, I could obfcrve nothing 

 but the pure heavens. Had a peifon, without fufpcfting any 

 ■thing of this ojjtie transformation, feen from the valley the 

 row of trees in the horizon evidently broken, and had again 

 feen from the hill \^ilhout obferving the gradual change 

 6. " durinsc 



