258 SUBDIVISIONS OF THE ARCTIC ZONE. 



On the other hand, it is no less remarkable how 

 the isothermal contours are deflected towards the 

 north, at certain points, as if they were the gates of 

 Nature, placed there by her own beneficent hand to 

 give entrance to those icy realms, where the empire 

 of frost under normal conditions holds perpetual sway. 



Professor Meyen, for this reason, in his division of 

 the earth into Climatic Zones, has subdivided the great 

 region thus periodically invaded by the arctic winter, 

 into no less than four distinct areas, which he has 

 named "The Colder Temperate Zone " (4.5 to 58 Lat. 

 N. and S.), " The Subarctic Zone " (Lat. 58 to the Arctic 

 and Antarctic Circles 66 32' N. and S.), "The Arctic 

 Zone " (from Lat. 66 32' N. and S. to Lat. 72), and 

 " The Polar Zone " (all tracts of land beyond Lat. 72 

 N. and S.) ; * his object being to define, as accurately 

 as possible, the geographical limits of the plants etc., 

 contained therein. 



We have however, contented ourselves with a much 

 simpler division, embracing the last two of Professor 

 Meyen's in what we have called " The Arctic Zone, " 

 but always subject to the reservation, which we have 

 not failed constantly to insist upon in tracing the 

 limits of all our terrestrial zones, that nowhere are 

 there any hard and fast lines, at which we can set 

 bounds to the climatic changes of Nature, or say 

 " Thus far, but no further ; " on the contrary, ex- 

 perience shows that local circumstances often involve 

 far-reaching exceptions and changes, which it is our 

 duty to recognise and point out, endeavouring at the 

 same time, to trace the effects to their moving causes 



* Outlines of the Geography of Plants, by Franz J. F. Meyen, M.D., 

 Professor of Botany at the University of Berlin, 1846, pp. 1 6 1 22O. 



