102 Dr. H. Schlagintweit's Observations in the Alps 



The foregoing table shows, that for different points of the 

 same vertical circle the decrease of the blue is accompanied by a 

 decided increase of the ochre. The ochre appeared strongest at 

 the horizon of the Grossglockner. The atmosphere in this por- 

 tion had therefore a slight tint of green*,, which. resulted from 

 the blending of the three colours, blue, yellow and white. 



"White objects seen from a distance have always a yellowish or 

 reddish tint imparted to them by the atmosphere. This is plainly 

 observable on clouds, houses, snow-covered slopes, &c. It is a 

 general rule, that, in the painting of such objects, a little ochre 

 must be added to the white. The colour of the brightest cloud- 

 masses, even when the sun is in a high position, contains gene- 

 rally from 1 to 2 per cent, of ochref. Distant mountains often 

 appear blue when the sun is opposite ; their own colour seems 

 to have some influence in this case, as the same mountains in 

 winter when covered with snow show a reddish-white colour J. 

 Those summits of the Alps which are covered with perpetual 

 snow, when seen from a great distance in direct sunlight, exhibit 

 this reddish tinge blended with the whiteness. 



The colouring of the light by its transmission through the 

 atmosphere is peculiarly remarkable in the hues exhibited by the 

 sky at daydawn and at sunset — the morning and the evening 

 red. Forbes § was the first to connect these beautiful colours 

 with the existence of watery vapour in a certain state of conden- 

 sation. The phenomenon of the morning and evening red is of 

 too intense and changeable a nature to be investigated by means 

 of our cyanometer. The evening glow of the Alps is peculiarly 

 well known as a splendid exhibition of the evening red. It 

 begins soon after sunset ; the precipices and snow-crowned sum- 

 mits assume a dazzling glow, which disappears almost instantly 

 when the shadow of the earth has attained the heights. A 

 second glow is often observed, particularly in the more southern 

 alpine groups ; on Mont Blanc, Monte Rosa, &c. it is exhibited 



* A strong green colour (grass- or bottle-green) may sometimes be ob- 

 served, at considerable elevations above the horizon, on clouds and moun- 

 tain peaks when glowing with intense red. This has been often observed 

 by Brandes and others. The phsenomenon is merely a subjective colouring, 

 occasioned by the wearying of the eye in gazing on the shining red. The 

 complementary green is observed more frequently and plainly when the eye 

 is directed, not on the firmament, but upon white objects. 



t The clouds sometimes exhibit a very dark hue — thunder-clouds, for 

 example. Sometimes the very finest of them cause important alterations 

 in the colour of the heavens, without being recognizable as distinct groups. 

 Humboldt has also observed such masses. — Voyages, vol. iii. p. 318. 4to. 



X Compare also Saussure's Voyages, vol. iv. § 2088, note 1 . 



§ " On the colour of Steam under certain circumstances." — Philosophical 

 Magazine, vol. xiv. pp. 121, 419 ; and Pogg. Ann., vol. xlvii. p. 593; and 

 supplementary volume, vol. i. 1842, p. 49. The last memoir contains an ex- 

 tensive collection of the earlier notions entertained upon this subject. 



