On the 20th of January the thermometer fell again, and
remained below the freezing point till the 12th of February: some of the
ice did not disappear till the following month.
When the ice had lain a short time, cracks appeared on the surface
exposed to the sun, and spread like a network from the edges towards the
centre of the surface. At first there was no regularity in the
connection of these lines, and the several meshes were of very different
sizes. After a time, the larger meshes split up into smaller, and the
system of network was found to penetrate below the surface, the cracks
deepening into furrows, which descended perpendicularly from the
surface, and divided the ice into long thin rhomboidal pillars. The
surface-end of some of these pillars was strongly marked with right
lines parallel to one of the sides of the mesh, and it was found that
there was a tendency in the ice to split down planes through these lines
and parallel to the corresponding side-plane. Parallel to the original
surface of the mass of ice, the pillars broke off evenly.
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