CHAPTER XIII. 



MOUNTAINS AND FJELDS. 



It inay have been observed that in the details given in 

 regard to the geographical distribution of different kinds 

 of forest trees in Norway, mention is made chiefly of 

 latitude, but the fact that such distribution is affected by 

 altitude as well as by latitude must not be ignored. There 

 is a co-relation between the two in so far as temperature is 

 concerned ; and it is mainly in relation to temperature 

 that the relation of altitude in different localities at which 

 different trees grow becomes of importance in discussions 

 connected with this fact. But the difference observable 

 is not related to this exclusively. The soil is generally 

 different in the plain, and even at the base of a moun- 

 tain, from what it is on the sides, and on the summit of 

 that mountain ; and there is also a difference in the 

 atmospheric pressure at a high altitude, and at the level 

 of the sea, and at all intermediate altitudes, which differ- 

 ence of pressure may not be without effect on the geo- 

 graphical distribution of trees. 



To the establishment and acceptance of this as a fact, 

 it is not necessary that we should know how it is that 

 it produces the effect ; it is a fact determined by observa- 

 tion ; and it may be seen on the ocean as well as on dry 

 land. 



' The ocean, as well as the land/ writes Balfour, ' possesses 

 its vegetable forms, which are of a peculiar kind, and exist 

 under different conditions of pressure, of surrounding 

 medium, and of light. Some sea- weeds, Harvey remarks, 

 are cosmopolitan or pelagic, as species of ulva and enterow 

 morpha, which are equally abundant in high northern and 



