'This makes it clear why at the northern and southern limits the pieces or ice-floes are comparatively small, whilst in the middle the floes may be two or three miles across; and why the pack may and does consist of various natures of ice-floes in extraordinary confusion.
'Further it will be understood why the belt grows narrower and the floes thinner and smaller as the summer advances.
'We know that where thick pack may be found early in January, open water and a clear sea may be found in February, and broadly that the later the date the easier the chance of getting through.
'A ship going through the pack must either break through the floes, push them aside, or go round them, observing that she cannot push floes which are more than 200 or 300 yards across.
'Whether a ship can get through or not depends on the thickness and nature of the ice, the size of the floes and the closeness with which they are packed together, as well as on her own power.
'The situation of the main bodies of pack and the closeness with which the floes are packed depend almost entirely on the prevailing winds. One cannot tell what winds have prevailed before one's arrival; therefore one cannot know much about the situation or density.
'Within limits the density is changing from day to day and even from hour to hour; such changes depend on the wind, but it may not necessarily be a local wind, so that at times they seem almost mysterious. One sees the floes pressing closely against one another at a
