1 62 Optical Phenomenon seen in Gle^mre. [Sess. 



coming under the former class, is the rainbow, which, speaking 

 in a very general way, is due to the refraction and reflection 

 of light on drops of water. Much more uncommon is the 

 lunar rainbow, which doubtless many of us have seen. Tliis 

 comparatively rare but very beautiful phenomenon differs 

 from the solar simply in the source and intensity of the light 

 producing it ; and being only visible at night, the distinction 

 of colours is very difficult to make out, and unless the circum- 

 stances are favourable, little else is seen than a pale gleam 

 of sickly white or yellow light. Anthelia proper are those 

 appearances consisting of a shadow surrounded by coloured 

 rings or bands thrown upon mist. Of these there are some 

 which, to the inhabitants of mountainous regions, possess the 

 characteristics of a supernatural intervention, and foster 

 superstitious cravings. Even now, when the days of legend 

 and superstition have passed away, and science has stripped 

 these phenomena of their marvellous character, and left their 

 names merely, mimis their meaning, they are watched by the 

 traveller and the scientist as closely as when they were 

 attributed to a supernatural agency. The most widely known 

 of these is that named the " Spectre of the Brocken." The 

 Brocken is the highest mountain of the Hartz chain, running 

 through Hanover. Its height is given as 3300 feet above 

 sea-level. It is stated that a traveller named Hane ascended 

 no less than thirty times to the summit before he contemplated 

 the object of his curiosity. In 1862 a French artist, M. 

 Stroobant, witnessed and carefully sketched this phenomenon. 

 He reached the summit just as the rising sun enabled him to 

 distinguish objects clearly at a distance. In his description 

 he says : — 



My guide, who had for some time appeared to be walking in search of 

 something, suddenly led me to an elevation, whence I had the singular 

 privilege of contemplating for a few instants the magnificent effect of 

 mirage which is termed the Spectre of the Brocken. The appearance is most 

 striking. A thick mist, which seemed to emerge from the clouds like an 

 immense curtain, suddenly rose to the west of the mountain, a rainbow was 

 formed, then certain indistinct shapes were delineated. First, the large 

 tower of the inn was reproduced upon a gigantic scale ; after that we saw 

 our two selves in a more vague and less exact shape, and these shadows 

 were in each instance surrounded by the colours of the rainbow, which 

 served as a frame to this fairy picture. 



