HUMMOCKING, 
385 
As long as we continued in Wellington Channel, 
our ice had not acquired its full firmness and tenac- 
ity: its structure was granular and almost spongy, 
its mass infiltrated with salt water, and its plasticity 
such that it crumbled and moulded itself to our form 
under pressures which would otherwise fiave destroy- 
ed us. 
By the time we had reached the middle of Barrow's 
Straits, and the winter's midnight of December had 
darkened around us, our thermometers indicating a 
mean of 15° and 20° below zero, the ice attained a 
thickness of three feet, with an almost flinty hard- 
ness, and a splintery fracture at right angles to its 
horizontal plane. Such ice was at its surface com- 
pletely fresh, and, when tested with nitrate of silver, 
gave not the slightest discoloration. 
It was here, while drifting at a mean rate of twelve 
miles a day, through a channel compressed by the 
salient projection of the shore, that the most fearful 
of our ice-disruptions occurred. They seemed to com- 
bine the horrors of tempest, explosion, and earth- 
quake. Our floe was severed to its centre. Dark 
rivers, exhaling that curious meteor, the frost-smoke, 
reticulated the entire surface ; and our vessel, thrown 
alternately upon her beams, or plunged bows down 
into the ice, impressed us with a sense of immediate 
destruction. 
This convulsion gave me an opportunity of witness- 
ing, upon a scale which perhaps exceeded that of any 
previous experience, the operation called hummocking. 
Imagine the flat, sn,ow-covered floe surface, caught 
between two forces of great intensity, or two moving 
bodies several feet in thickness and miles in diame- 
ter, meeting at their marginal lines. The pure white 
Bb 
