THE SPRIXG AND SU AIMER OF iSg^ 457 



The open spaces, the lanes, and the rifts in the ice are, 

 of course, produced, like the pressure and packing, by 

 the shifting winds and the tidal currents that set the ice 

 drifting first in one direction, then in another. And they 

 best prove, perhaps, how the surface of the Polar Sea 

 must be considered as one continuous mass of ice-f^oes 

 in constant motion, now frozen together, now torn apart, 

 or crushed against each other. 



During the whole of our drift I paid great attention to 

 this ice, not only with respect to its motion, but to its 

 formation and growth as well. In the Introduction of 

 this book I have pointed out that, even should the ice 

 pass year after year in the cold Polar Sea, it could not 

 by mere freezing attain more than a certain thickness. 

 From measurements that were constantly being made, 

 it appeared that the ice which was formed during the 

 autumn in October or November continued to increase 

 in size during the whole of the winter and out into 

 the spring, but more slowly the thicker it became. On 

 April loth it was about 2.31 metres; April 21st, 2.41 

 metres; May 5th, 2.45 metres; May 31st, 2.52 metres; 

 June 9th, 2. 58 metres. It was thus continually increas- 

 ino; in bulk, notwithstandino^ that the snow now melted 

 quickly on the surface, and large pools of fresh water 

 were formed on the floes. On June 20th the thick- 

 ness was the same, although the melting on the sur- 

 face had now increased considerably. On July 4th the 

 thickness was 2.57 metres. On July loth I was amazed 



