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



colours which actually appear, and to give the per-centage con- 

 tent of these. The whole of the colours thus obtained were laid 

 upon strips of strong paper, 2 centims. wide and 6 centims. long. 

 These were fastened together in three small but rather wide books, 

 so that they took up in each case three of the edges, while a 

 small uncoloin'ed strip within contained the description of the 

 mixture. The coloured papers were separated, each from its 

 neighbour, by an interposed sheet, as otherwise the sudden open- 

 ing of the book would be accompanied by a separation of the 

 colour. The same series might also be attained with the rotating 

 disc, if, instead of the third blue sector, one of ochre was substi- 

 tuted. The latter process, however, was more rarely resorted to 

 in the determination of the colours of the clouds than in finding 

 the depth of the atmospheric blue. In the case of clouds, the 

 greater number of compound colours would have delayed the ex- 

 periments too much; and the result, on account of the sub- 

 jective peculiarities of the eye itself, would still be only approxi- 

 mative. 



In stating the observations, wc will begin with the simplest, 

 that is to say, with those in which the mere per-centage of cobalt 

 is given. Besides the zenith, which was in every case examined, 

 we sometimes made determinations of the side portions of the 

 firmament. The latter were always so chosen, that they lay 

 directly opposite the position of the sun at the time. Their 

 zenith distance is contained in the sixth column. The experi- 

 ments were made in 1847 and 1848. 



Observations with the Cyanometer of two Colours (No. I.). 



