NO. n.] 



THE TEMPERATURE OF THE POLAR ICE. 



565 



The Briggsian logaritlimic decrement 0'2026 corresponds to the Napierian 

 logarithmic decrement 0'4662. According to the theory, this number should 

 be equal to the retardation of the phase. Thus the retardation 

 from the ranges = 0-4662 radian = 26-° 78 



- phase-angles =0-2557 „ = 14-°65. 



The theory requires the identity of these two numbers. 



This requirement is not fulfilled. 



The phase-angles give a retardation of 14-86 days per metre. The velocity 

 with which the heat-wave is propagated in the ice becomes 24-58 metres in 

 one year, or 6-729 centimetres in one day. 



7t i 



The thermometric conductivity K is equal to -^ • -sf. 



Putting T = 1 year = 365-25 X 24 X 60 minutes and r in centimetres, 

 we have 



fi-om the phase-angles r = 0002557 £"=0-91 pr. cm. and min. 

 „ . ranges r = 0004662 K = 21 - „ - „ 



Hann gives (L. d. M. p. 741) for ice, £"=0-68. 



The value derived from the phase-angles is nearest to this value. iL^O-68 

 gives r = 17° instead of our 14'° 65, but it is very near to the otherwise found 

 16-°3 (p. 564). 



We have seen that the depth which the heat-wave attains in one year, 

 computed from the phase-angles, is 24-6 metres. To this depth the polar-ice 

 does not reach; its thickness is only about 3 metres. Below the ice is sea- 

 water, the temperature of which is nearly constant throughout the year. At 

 the depth of 3 metres. Professor Nansen gives the following temperatures ^ 



May, November and December are perhaps a little too low. Prof. 

 Nansen names August as the month of maximum. The minimum probably 

 occurs at the end of the winter, or the beginning of spring. The whole 

 annual variation seems only to be from — l-''5 to — 1-°7, or to have a range 

 of only 0-°2 or even less. 



' Norw. Polar Exp. Vol. Ill, No. 9. Oceanography of North Polar Basin, p. 314. 



