TIDES AND CURRENTS. 677 



" During a year and a half the explorers had constant oppor- 

 tunities closely to observe the behaviour and formation of pack- 

 ice. The phenomenon is instructive, as it is^the same in the whole 

 of the Arctic regions. With the exception of land-ice, which 

 clings to the coasts and never reaches far out into the sea, all ice — 

 icebergs as well as fields — is in constant motion, winter and 

 summer ; and this, as has been shown, is through the influence of 

 winds. The motion, however, is a different one almost with every 

 field, and thus a certain pressure results wherever two fields touch ; 

 this naturally leads to the breaking up of the fields, and the con- 

 traction of the ice during sudden low temperatures plays its part 

 in a similar way. If one considers the great extent of the fields, 

 sometimes of many miles, and their enormous masses, one can 

 easily imagine the colossal forces which are active in these 

 phenomena, and the greatness of their effects. When two fields 

 meet, a combat body to body ensues, often lasting only a few 

 minutes, but sometimes even for days and weeks. The edges are 

 then turned up on both sides, upwards and downwards, an ir- 

 regular wall of ice consisting of wildly-mixed blocks begins to 

 build itself, the pressure increases more and more, masses of ice 

 eight feet long and broad are lifted 30 to 40 feet high, and then 

 fall to make room for others. At last one of the fields begins to 

 shift itself for some distance underneath the other one ; often they 

 separate for a while only to renew the struggle. But the end of 

 it always is that the intense cold unites all into one solid mass ; a 

 single field results from the two, and the next storm or quick 

 change of temperature cracks the new fields in some other direc- 

 tion, the pieces renewing the old struggle. This is the origin of 

 the ice-fields, which are quite irregular above and below, some- 

 times only consisting of blocks that have frozen together, and 

 filling up the whole Arctic region as so-called joack-ice. 



" During winter, snow-storms fill up all smaller irregularities 

 completely. As soon as the sun begins its action, the crushing 

 of the ice decreases, the winterly ice walls diminish considerably, 

 immense masses of ice and snow are melted, and the resulting 

 sweet water forms large lakes on all the lower even parts of the 

 field. During the summer, about four feet of ice are thus melted 

 down from above ; of course the whole field and everything upon 

 it — the explorer's ship, for instance — is raised so much higher. In 

 the following winter it grows below in the same ratio, and thus the 

 whole of the ice is in an iminterrupted process of renovation, from 

 below upwards; we may conclude that all the old pack-ice is 

 replaced by new in the course of two years. 



" The spaces of open water which naturally occur during the 

 great crushes are soon again covered by fresh ice in winter ; the 

 intense cold keeps repairing the broken field of ice. Lieut. 

 Weyprecht observed that within 24 hours, and with a tempe- 

 rature of -30° to 40° R. (37-5-50° C.,) the new crust becomes 

 about a foot thick. The salt of the sea-water has not time to be 

 displaced entirely, the formation of ice going on too quickly, and 

 a considerable quantity freezes into the upper strata of the ice ; 

 this quantity decreases downwards as the ice takes more time to 



