456 THE YERMAK ICE BREAKER. 



It is quite another proceedina-, breakinof the polar ice. In some 

 places of the Baltic the ice field is uiiiMterrui)ted from one shore to 

 another. In the arctic seas the ice is broken. Floes of ice might be 

 several miles or several fathoms in lenoth. Between ice floes are the 

 lanes, which are very irregular. Sometimes ice floes are pressed 

 against each other and sometimes not. When the ice is not pressed, 

 the progress of the ship is very easy. Floes of ice even a mile long 

 move away and give passage to the ship. The sharp, projecting 

 angles of the floes break very easily, and sometimes it is preferable to 

 shorten the way by cutting a floe right through. Thick polar ice looks 

 very heavy and .strong, and when walking on it one can not imagine 

 that such a heavy thing could be broken. But the fact is that even 

 ice 14 feet thick cracks when charged at by the ship, provided there 

 is room to remove ])roken parts. 



The lower part of the polar floe has constantly, more or less, the 

 same temperature, while the temperature of the surface varies with 

 the temperature of the air, which sometimes produces the cracks and 

 sometimes prepares the ice for cracking. The moment the ship 

 charges the ice it cracks at the place at which it might crack in half 

 an hour itself with another change of temperature of a degree or so, 

 or with the beginning of pressure. The big floe cracks more easiW 

 than the small floe, which sometimes is pushed bj?^ the ship and goes 

 in front until it manages somehow to pass on one side of the ship or 

 the other. 



Fields of hunnnocky ice are liable to crack even more than flelds of 

 plain ice. In charging that ice the ship's bow rises to 9 feet; then 

 the fleld cracks, the ship falls down and goes ahead, moving aside the 

 debris of the ice fleld. It is a most exciting scene to see some of the 

 big pieces of ice falling down into the water and the others coming to 

 the surface from a great depth, every detached piece trying to And a 

 new position, while the ship itself, ])eing always pushed ahead b}' her 

 machiner3% gradually advances, maybe rises again, and gives another 

 crack to the fleld ice. We took some cinematograph pictures, which 

 show how much the ship lifts herself up in the ice, and that gives us 

 means of calculating what weight is applied to crack the floe of ice. 

 If the ice is in the period of pressure, progress is not so easy. On one 

 occasion it took me four hours to make 2 miles, while usually the ship 

 went, by zigzags, with a speed of 3^ knots, making good '2^ knots an 

 hour. 



There is a great difference in ice-breaking in the Baltic Sea and the 

 polar regions. Hummocks in the Baltic Sea are never high above 

 the level, but sometimes they are very deep. According to our meas- 

 urement, they go down to as much as 20 feet. On one occasion we 

 measured 27 feet down and 6 feet up, the total being 33 feet. Such 

 hummocks are composed of pieces 1 to 3 feet thick. Many hum- 



