from The Century Dictionary and Cyclopedia
- n. Ice left suspended by the withdrawal of the water beneath.
Sorry, no etymologies found.
Starting in the grey dawn, for mile after mile we had to haul the sled over crumbly shell-ice that broke through to gravel; and when the shell-ice was done we came to a new bend where a rapid current washed a steep mud bank.
At times, for a few hundred yards, the sled would glide with little effort over smooth, polished ice; then would come a long sand-bar, the side of which we had to hug close, and the ice upon it was what is called "shell-ice," through several layers of which we broke at every step.