Q. Are there not October gales which often separate the bummocks of ice and allow ships to pass on! - A. Decidedly. I do not know what the direction of the wind was at the time, but if the wind was going from the land, then he would[…]
Source: wiktionary
The ice "bridge" which broke was formed of great bummocks of ice welded together at the foot of the great cataract, […]
Source: wiktionary
The most important ice features are the frequency and extent of downward projections (bummocks and ice keels) from the underside of the ice canopy (pack ice and enclosed water areas from the point of view of the submariner)[…]
Source: wiktionary