887 



of any given place, according lo the geographical position of the 

 islands and tlie local lopographical conditions. The frequency of 

 fog has ah'eady heen referred to, and the amount of Hght available 

 on foggy days is of course comparatively limited. In addition, the 

 atmosphere is ahiiost constantly more or less overcast. The mean 

 amount of cloud is about 7,4 (scale 0-10; O = clear; 10 = com- 

 pletely overclouded). In other words three-fourths of the sky on 

 an average are covered with clouds. There are annually only 18 

 clear days (O — 2 of the scale), but 184 »dark« days with the sky 

 entirely cloudy are recorded. The full effect of the sun is lost from 



IS Mountain pliiteau on Kirkeborejn on Stronio. Bare »Rudemark« showing large and small 

 slones blown togethcr into the cracks. (From photo. by Author). 



this cause, and an additional loss results from the high northerly 

 latitude of the islands. The angle of incidence of the sun's rays 

 to the earth's surface at noon in winter is only 5", and this only 

 holds good if the surface is flat, a rare circumstance on the Færoes 

 where almost the whole surface is more or less sloping. According 

 to the exposure of the slope the vegetation receives light, together 

 with heat, to a greater or less extent than on a flat surface. A 

 slope facing south is thus more favourably situated in this respect 

 than one facing northwards, and a marked difference in the com- 

 position of the vegetation is the result. The southern exposures 

 carry a great wealth of flowering piants, while the northerly ex- 

 posures have a larger proportion of mosses. The Calluna or 

 heather moors of the islands, for instance, are always met with 

 on slopes facing southwards; similarly the rock-terraces (»Hamre«) 

 towards the south always have the greatest variety of flowers. It 

 follows naturally that piaces of this kind offer the best climatic 



