810 
MR J. M. WORDIE ON THE NATURAL HISTORY OF PACK-ICE 
and less plastic were on that account less bendable; the ice swelled up, a crack 
formed perpendicular to the direction of the. pressure, and a tent-like structure 
resulted. Other radiating cracks were usually developed ; and, if movement 
^continued, the blocks so formed were soon piled up into a pressure ridge. 
(c) Rafting was the commonest of all the processes, and followed automatically 
when either of the other two methods already mentioned was carried to an extreme. 
Moreover, when rafting was going on, there was often a good deal of bending and 
tenting also taking place. In very thin ice, for instance, a process of rafting was 
developed in conjunction with bending, and gave a somewhat peculiar appearance 
to young newly-frozen leads, namely a series of lines at or nearly at right angles 
to the edge of the lead. This was due to the young-ice closing up when not more 
than 1 to 2 inches thick ; the two sheets dovetailed into one another, like moving the 
fingers of one hand over those of the other, in such a way that the little finger of 
the right hand is above the little finger of the left, the third finger below, the middle 
above, the first below, and so on. The vertical grain of young-ice allowed of the 
process going on to a considerable distance, and in this way two sheets of young-ice 
might dovetail to a depth of 5 to 10 yards. 
This was rafting at its very simplest. A slightly more advanced stage occurred 
where the screwing tendency brought jutting corner against corner, and forced one 
floe to override the other. Most impressive of all, however, was the formation 
of a great pressure ridge. Whether the work of a few hours, or a matter of days, it 
was the most forceful and exciting incident of life on the pack. One case is worth 
describing in detail : namely the occurrences in July 1915, which lasted for nearly 
a fortnight and exhibited in that time all possible types of “ hummocking.” 
About 300 yards forward of the ship’s bows a lead had formed in February 1915, 
and when frozen over with level young-ice had been found on that account the 
most convenient place on which to train the dog teams. By the latter half of 
March, however, a number of cracks had already formed across this lead (fig. 3), 
and their closing had led to a certain amount of light pressure. It was not, however, 
till July 14 and 15, as a result of a strong S.W. blizzard, that the topography 
ahead changed to any great extent. On these dates the floes broke up and re- 
arranged themselves ; and in one case a small berg moved half a mile from its 
former position and swung round through 90 degrees. The result was that the 
ice-topography, with the exception of the 300 yards immediately ahead, was com- 
pletely changed. It now consisted of islands of old pack-ice set among young-ice 
of two to three days’ growth, the latter with a rough, uneven surface due to the 
overlapping of small pancakes. Pressure at this time, it should be noted, did not 
involve the older floes. For the next few days the ice was very restless, and the 
small berg already mentioned moved back very nearly to its former position relative 
to the ship, and at the same time swung a further 90 degrees. 
The ice immediately surrounding the ship was in its component parts at least 
