ELECTRICAL CONDITIONS OF GREAT COLD. 331 



is as a rule followed everywhere throughout the tem- 

 perate zones by the decline and fall of the leaf of 

 deciduous trees, and by the arrest of vegetable growths ; 

 thus producing an interval of rest for plants, which is 

 almost as essential for their well-being as it is for 

 men and animals; it is not however so generally 

 known that this period of rest is as efficiently created 

 by heat as by cold. In tropical and sub-tropical lands 

 for example, where there is a long dry season, we 

 have already shown that combined heat and drought 

 will cause the fall of the leaf from trees and plants, 

 exactly as the cold does in northern regions, and they 

 subsequently remain bare of foliage until the return of 

 the rains again starts them into growth; the advent 

 of the rains therefore represents our spring in these 

 countries. Even in the equatorial zone an artificial 

 period of rest can be produced for trees imported 

 from temperate regions, by exposing the roots to the fierce 

 heat of the sun during short intervals of dry weather. 



In our section on the Equatorial Zone this matter 

 has been gone into at greater length, and further 

 details about it will be found there. 



The highly charged electrical condition of the 

 atmosphere in the arctic regions, though thunderstorms 

 are rarely or never seen there, in many respects also 

 bears a close resemblance to the results following upon 

 the intense dry heat of the desert zone; in both cases 

 the dryness of the atmosphere is very remarkable, 

 and in each, the phenomena of sparks emitted by 

 woollen garments, etc., is reproduced. * Thus during 



* See Seas and Skies in Many Latitudes, by the Hon. Ralph Aber- 

 cromby, F.R.M.S., 1888, p. 8, and Sir John Richardson's Boat Voyage 

 through Rupert's Land, 1851, Vol. ii, p. IOI. 



