MOUNTAINS AND FJELDS. wah 
® Continuous zone, but-in extensive patches, some higher, 
some lower, all within a definite range, beneath which, 
only a little way, it is found impracticable to cultivate it. 
‘Such facts as have been cited seem, together, to warrant 
the supposition that atmospheric and oceanic pressure may 
possibly have some influence in permitting and preventing 
the growth of certain plants within and beyond a certain 
range. It may be that we can attribute to this but little 
influ :nce in comparison with the modification of light, and 
still more the modification of heat, produced by altitude 
above the level of the ocean, and depth below its surface. 
But be the operation of the influence what it may ;’and 
be. it the-case that it is only in the case of such modifica- 
tion of pressure, light, and heat, as are strongly marked, 
and are incidental to difference in altitude, that it arrests 
attention, such differences as are indicated in most locali- 
ties by. differences in barometric phenomena have comé to 
be valued in investigations of the natural history of these 
plants. 
The following is a summary of observations of the kind 
made in Norway, for which I am indebted to Dr Broch’s 
report :— : 
In estimating the barometric pressure of the atmosphere 
the calculation is made of what it would be in the locality 
at the level of the sea. The mean annual pressure attains 
its maximum towards the south-west of the Scadinavian 
peninsula. It has its minimum in the region from the 
Lofoden Islands to the North Cape, descending from 758 
mm. at Mandal to 753 at the place last mentioned. At 
Christiania the mean pressure of the air is 757.7 mm. 
‘Twice in the course of the last forty years it has been 786 
mm., and it has been seen as low as 721 mm. 
In winter the distribution of the pressure accords as a 
general rule with what it is on the average for the year. 
Greatest towards the south-east, the pressure decreases 
towards the south-west, the isobaric line passing through 
localities with equal barometric indications of atmospheric 
