340 Refie&ion and Refra&ion of Light 



country. Soon the fnow was feen to roll down the fides of 

 the mountains into the valleys beneath, and left the gray 

 rocks of the mountains naked and {harp. As the fun in- 

 creafed in power, the vapour vaniihed. On the left, the 

 river and adjacent country were alio covered with a vapour, 

 but of quite different appearance from the former. The 

 country feemed laid out in lawns and improvements, ii> 

 which were fituated three gentlemen's feats; the hotifes well 

 defined, the windows and doors diftinct ; fome of the win- 

 dows appeared open, and brafs knockers were feen on the 

 doors. From the houfes were beautiful fhrubberies bordered 

 with white Chineie paling; behind the fhrubberies were 

 forefts of pines ; and diftant mountains, in fine perfpective, 

 clofed the fcene. Before the houfes in the lawns were clumps 

 of fine foreft trees. In about half an hour two of the houfes 

 vanifhed, and the clumps in front difappeared, and in their 

 place a fine oak fprang up, which was the laft that quitted 

 the fcene. The fun becoming powerful, the vapour was ra- 

 refied, and the entire magic difappeared. 



The two former of the exhibitions of the fata morgana 

 were evidently caufed by the reflection of fome of the build- 

 ings and other parts of the town of Youghal in a denfe va- 

 pour or fog ftrongly illuminated by the fun. But in order to 

 have an adequate idea of the nature of the phenomenon, let 

 AG (fig. i.) be a fog bank or denfe vapour, whofe furface 

 next the fun is uneven, and formed of a variety of planes 

 capable of refle&ing light, as AB, BC, CD, DE, EF, and 

 FG. Let O be a houfe and tree. Now, by the laws of op- 

 tics, if a fpe&ator be fo fituated, as at I, that the refle&ive 

 rays proceeding from the incident ones OG, OF, &c. meet 

 the eye of the fpeclator at I, the image of the houfe and tree 

 at O will be multiplied into the town vr, in which, if the 

 furface DE is cylindrical and fomewhat irregular at the top, 

 the image of the houfe will be transformed into a tower, and 

 the roof into a fpire, with the chimney a flag. Alfo, if any 

 of the other plants be imperfect:, the images^ reflected there- 

 from will be imperfeel:, and the houfes appear in ruins. If 

 the fpe&ator moves from I to L, and during that time the 

 air mould change any of the furfaces, the representation will 

 be fomewhat changed ; the image of 0, from the plane DE, 

 will become a tower with a dome, and the whole will appear 

 as at xy. As the wind changes the form of the fog, or the 

 pofuion of the fun or clouds alters the lights, the entire re- 

 prelentation will difappear, or fufTer confiderable changes: 

 on which account none of thole aerial exhibitions continue 

 any length of time., and always in calm, weather and a clear 

 . 5 &Y> 



