879 



Fogs are also frequent, and take the place of rain, especially 

 during the summer months. The annual number of fog-days is 54, 

 of which 30 occur during the months of June, July and August, 

 whereas the months from December to March have only one foggy 

 day each on the average. It must be noted, however, that all these 

 meteorological observations have been taken in Thorshavn, con- 

 sequently in the lowlands. The number of foggy days amongst the 

 mountains is certainly much greater, but unfortunately no record of 

 these is available. 



The relative humidity of the atmosphere is great, namely 

 82 p. cent., p. annum. On comparing the figures for each month 

 it is found, that there is no great variation during the different sea- 

 sons. The lowest mean humidity, 78 — 80 p. cent., is during the 

 spring months, February to May; the greatest is in the summer, 

 July to September (85 p. cent.). 



The variation in the relative humidity is not, unfortunately, 

 indicated by these figures, but, through the courtesy of the »Da- 

 nish Meteorological Institute«, I have been able to consult a table 

 showing the lowest records of relative humidity observed. This 

 table States, that periods may occur, during which the humidity 

 falls to 30—50 p. cent., but this is exceptional (e. g. 30 p. cent. has 

 been observed only once in 25 years, and 31 to 39 only seven 

 times). The lower readings occur without relation to season, but on 

 the whole are more frequent in early summer. According to M. 

 Knudsen (1900), the humidity and the temperature are both de- 

 pendent upon the direction of the winds, or rather, whether the 

 wind comes from the »East-lcelandic polar stream«, or from the 

 »Gulf stream». When the wind blows from the polar stream, the 

 average relative humidity is 72 — 81 p. cent. ; if from the Gulf stream, 

 then 81 — 90 p. cent. is attained. Winds from the polar stream also 

 lower the temperature over the Islands to a considerable extent. 



Thus though the atmospheric humidity may become very low 

 on rare occasions, it is open to us to regard it as almost always 

 comparatively high. 



Under these conditions, and with the prevailing moistness of 

 the soil, there is no necessity for the development of structures, 

 such as dense hair-coverings, etc, which protect piants from the 

 effects of excessive evaporation. It is actually the case, as we shall 

 see later, that woolly or tomentose species are the exceptions amongst 

 Færoese piants ; in faet, xerophiious characters are exhibited by com- 



