The following table gives the approximate quantity of Red Cross 

 Extra Dynamite 40% required to break floating ice cakes of different 

 thickness when the dynamite is exploded on the surface of the ice. The 

 number of charges necessary depends on the size and extent of the ice 

 cake: 



To open ice gorges already formed, a channel should be cut through 

 them beginning on the down-stream side and working up stream along 

 the line of the strongest current. In large streams this channel should be 

 about fifty feet wide, and if the gorge does not move after the channel 

 has been cut through, it will then be necessary to begin at the down- 

 stream side of the gorge again and widen the channel until the ice has 

 been carried away. 



To make the channel, holes are cut with an axe, bar or ice spade 

 through the ice twenty to thirty feet apart. These holes are laid out in 

 a semi-circle with the two end holes about twenty to thirty feet back from 

 the open water and fifty feet apart. 



FIG. 136. DIAGRAM SHOWING LOCATION OF ROW OF HOLES FOR 

 BLASTING AN ICE GORGE 



158 



