78 FORESTRY OF NORWAY. 
in the interior of Nordland, and on the coasts of the pre- 
fectures of Tromso and of Finmark, is between 5 mm. and 
4 mm. In the environs of Roros, in Southern Norway, 
and in the interior of Finmark, it scarcely exceeds 4 mm. 
‘The quantity of aqueous vapour appears thus to depend 
primarily on proximity to the coast, where it is greatest ; 
but it depends also on the latitude and difference of tem- 
perature thus produced. , 
In the winter season the hygrometric lines are substan- 
tially similar to those of the mean of the year, In 
January the tension is that of 4 mm. at Christiansand, 
Bergen, Sondmor, Christiansand, and Bodo; 3 mm. in 
Smalenene, Inner-Sogne, Stjordal, and Sengen; 2 mm. 
on the Dovrefjeld, in the interior of Finmark, and in 
South Varanger. 
In summer the quantity of aqueous vapour is much 
more considerable than in winter, and the distribution of 
it over the country is somewhat different. In July the 
line of tension of 10 mm. passes through Mandal and 
Tonsberg, and over this extent it is in the month of July 
that the greatest quantity of aqueous vapour throughout 
the year is found. The line of tension of 9 mm. passes 
outside the west coast from Skudesnaes to Cape Stat, 
and there inclines to the north-east, taking a direction to 
the east of Alesund, and towards Christiansand. Thence 
it inclines towards the south, descending towards Inner- 
Sogne, Hardanger, it proceeds towards the east to 
Drobak, and finally passes into Sweden. The great 
inflection of this line indicates the excess of aqueous 
vapour on the west coast relatively to the interior 
regions of the fiords in Sogne and Hardanger. These 
regions, viewed in regard to the hygrometric condition, 
approximate that of the interior, where the line indicates 
a region relatively deficient in moisture. The transition 
from the embouchure to the head of the Christiania fiord 
is very much marked; there the tension diminishes from 
10°5 mm, to 86 mm.; it is the greatest variation seen in 
Norway. The line of tension of 8 mm, in July passes 
