THE YERMAK ICE BREAKER. 453 



pounds are required to break the same oblong. After this wo molted 

 the ice from different depths of the floe, and we tested the melting- 

 point. It proved to be very near to the freezing point of fresh water. 



The exterior part of the ice in water is spongy, with canals and holes 

 in it; it looks from the top like lace. The ice of this spongy part has 

 the lowest melting point visible, from 31.3° to 30.6°. We' subjected 

 the sea ice to the influence of a current of salt water, 29.8° F., and 

 found that ice melts in that temperature very easily. It is rather 

 remarkable that ice melts in water the temperature of which is more 

 than 2 degrees below its melting temperature. 



After the melting point of the ice was determined, we measured the 

 specific gravity of the liquefied ice; it was proved that this water con- 

 tained generally very little salt indeed. Surface ice gave almost fresh 

 water, but the ice at the bottom of the floe contained a little more salt, 

 salinity varying from 0.01 to 0.69. The latter high salinity is obtained 

 from the liquid ice of the spongy part of the floe. 



Direct measurement of the ice floes has shown that the ice i-idges 

 have generally the height of 10 to 14 feet. It is not unusual to meet 

 an ice ridge 16 feet high. One separate ice ridge was 22 feet high, 

 while on one occasion we saw a detached piece projecting something 

 about 6 fathoms. We did not reach it, and consequently could not 

 measure it, so that this last figure is estimated bj^ eye. 



There is no difficulty in measuring the superficial part of the ice, 

 but it is not so easy to obtain a proper knowledge of the depth to which 

 the ice ridges extend below the water line. The direct l)oring of the 

 ice gives good figures. We had an ordinary boring machine, but that 

 did not answer the purpose well enough, because the progress of boring 

 w^as rather slow. Then we arranged a steam jet, which melted a hole 

 in the ice, and answered the purpose admirably; but unfortunateh' we 

 were short of pipes, and could not reach the lowest part of the ridgos. 

 The direct boring showed the thickness of ice and water layers, or 

 spaces in the direct vertical line. These are the figures: 



First boring— Seooud boring— 



12 feet ice. 21 feet ice. 



2 feet water. 2 feet water. 



3 feet ice. '-^ fw'^ '<'f ■ 

 2 feet water. — 



4 feet ice. Total, 26 feet. 



Total, 23 feet. 

 Then we tried to pass under the ice ridges a float witli Thomson's 

 sounding tube attached to it. We put the float on one side of the ice 

 floe and passed the rope around it to the other side. A little weight 

 was generallv attached at 1 fathom distance from the float, ^^'hon the 

 rope sank properlv we pulled it to the other side of the floe. Some- 

 times all this maneuver was done with the boat and sometimes with the 



