Optical Phcenomena seen in Switzerland. [i'i5 



be, some long heaths or furze will play the part of our alpine 

 forests; and I would advise you to try to place a bee-hive in 

 the required position, and it would perfectly represent our 

 swallows, sparks or stars. 



I now only wonder that such a phaenomenon, which must 

 necessarily take place in every mountain of the earth, every 

 day and at every hour of the day when the sun shines, should 

 never have been noticed before. 



I now come to another subject which you also desired me 

 to mention : I mean the varying colours exhibited by Mont 

 Blanc during and after sunset. Lord Minto was perfectly 

 right in the account he gave you of these appearances. But 

 he may have omitted some circumstances which will assist in 

 leading us to an explanation of these vai'ying appearances. 

 I shall here state the facts in the order in which they appear. 

 When the sun is near setting, and the weather is serene, all 

 the mountains of the Alps, facing the west, are tinged with 

 a fine purplish hue, which on Mont Blanc, on account of its 

 bright covering of snow, takes a tinge more verging towards 

 a light orange. When the sun has set for the plain, these 

 mountains appear more vivid and more illuminated, by the 

 effect of contrast. When, some minutes after, the lower 

 mountains are in the shade, their purple hue is changed into 

 a dark blueish tinge, the contrast between their shaded parts 

 and those that were lighted by the sun has disappeared, and 

 an almost uniform grayish blue shade covers them all ; at 

 this time Mont Blanc remains the only terrestrial object still 

 lighted by the rays of the sun, and that circumstance causes 

 its immense mass of snow to appear more bright, and its yel- 

 lowish orange colour more vivid : at the same time the con- 

 trast between the projected and other shadows and the lighted 

 parts is at its maximum (I have two or three times seen 

 Mont Blanc at that moment, and when dark clouds were be- 

 hind it, look almost as bright and red as a live coal). When, 

 however, the sun has set for Mont Blanc, which happens 

 about a quarter of an hour after it has set for the plain round 

 Geneva, then the whole of MontBlanc assumes a dull blueish 

 white hue, and a flattened appearance, owing to the absence 

 of contrast from the once shaded parts with those that were 

 lighted. And so its new aspect is to that which it offered a ^cw 

 minutes before, like that of a dead body to a living and healthy 

 one. This pale and, as it were, morbid appearance of the 

 mountain is owing to the fact, that above it exists still a wide 

 zone of atmosphere loaded with thin and light vapours, for 

 which the sun has not yet set, and which on that account are 

 still lighted vividly, and coloured with a purple hue. When, 



