76 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 8*6 mm. ; it is the greatest variation seen in 

 Norway. The line of tension of 8 mm. in July passes 



