Now the plate D is placed at an angle of 53° 11´ and C at an angle of 56° 45´, so that when a film of water is breathed upon them the light will be reflected from the latter, and none from the former; that is, the act of breathing upon the plates will restore the invisible and extinguish the visible image. LETTER VI. Natural phenomena marked with the marvellous--Spectre of the Brocken described--Analogous phenomena--Aërial spectres seen in Cumberland--Fata Morgana in the Straits of Messina--Objects below the horizon raised and magnified by refraction--Singular example seen at Hastings--Dover Castle seen through the hill on which it stands--Erect and inverted images of distant ships seen in the air--Similar phenomena seen in the Arctic regions--Enchanted coast--Mr. Scoresby recognizes his father’s ship by its aërial image--Images of cows seen in the air--Inverted image of horses seen in South America--Lateral images produced by refraction--Aërial spectres by reflexion--Explanation of the preceding phenomena. Among the wonders of the natural world which are every day presented to us, without either exciting our surprise or attracting our notice, some are occasionally displayed which possess all the characters of supernatural phenomena. In the names by which they are familiarly known, we recognize the terror which they inspired, and even now, when science has reduced them to the level of natural phenomena, and developed the causes from which they arise, they still retain their primitive importance, and are watched by the philosopher with as intense an interest as when they were deemed the immediate effects of Divine power. Among these phenomena we may enumerate the _Spectre of the Brocken_, the _Fata Morgana_ of the Straits of Messina, the _Spectre Ships_ which appear in the air, and the other extraordinary effects of the _Mirage_.[14] [14] In the Sanscrit, says Baron Humboldt, the phenomenon of the Mirage is called _Mriga Trichna_, “thirst or desire of the antelope,” no doubt because this animal _Mriga_, compelled by thirst, _Trichna_, approaches those barren plains where, from the effect of unequal refraction, he thinks he perceives the undulating surface of the waters.--_Personal Narrative_, vol. iii., p. 554.