In these troubled areas I had frequent opportunities to measure ice-thickness. From my observation I had come to the conclusion that ice does not freeze to a depth of more than twelve or fifteen feet during a single year. Occasionally we crossed fields fifty feet thick. These invariably showed signs of many years of surface upbuilding.
It is very difficult to estimate the amount of submerged freezing after the first year's ice, but the very uniform thickness of Antarctic sea ice suggests that a limit is reached the second year, when the ice, with its cover of snow, is so thick that very little is added afterward from below.
Increase in size after that is probably the result mostly of addition to the superstructure. Frequent falls of snow, combined with alternate melting and freezing in summer, and a process similar to the upbuilding of glacial ice, are mainly responsible for the growth in thickness of the ice on the Polar sea.
The very heavy, undulating fields, which give character to the mid-Polar ice and escape along the east and west coasts of Greenland, are, therefore, mostly augmented from the surface.
Continuing north, at no time was the horizon perfectly clear. But the weather was good enough to permit frequent nautical observations. Our course was lined on uninteresting blank sheets. There were elusive signs of land frequent enough to maintain an exploring enthusiasm, which helped me also in satisfying my companions. For thus they were encouraged to believe in a nearness to terrestrial solidity. At every breathing spell, when we got together for a little chat, Ah-we-lah's hand, with pointed finger, was directed to some spot on the horizon or some low-lying cloud, with the shout of "Noona?" (land), to which I always replied in the affirmative; but, for me, the field-glasses and later positions dispelled the illusion.
Man, under pressure of circumstances, will adapt himself to most conditions of life. To me the other-world environment of the Polar-pack, far from continental fastness, was beginning to seem quite natural.
We forced marches day after day. We traveled until dogs languished or legs failed. Ice hills rose and fell before us. Mirages grimaced at our dashing teams with wondering faces. Daily the incidents and our position were recorded, but our adventures were promptly forgotten in the mental bleach of the next day's effort.
Night was now as bright as day. By habit, we emerged from our igloos later and later. On the 5th and 6th we waited until noon before starting, to get observations; but, as was so often the case, when the sun was watched, it slipped under clouds. This late start brought our stopping time close to midnight, and infused an interest in the midnight sun; but the persistent haze which clouded the horizon at night when the sun was low denied us a glimpse of the midnight luminary.
The night of April 7 was made notable by the swing of the sun at midnight, above the usual obscuring mist, behind which it had, during previous days, sunk with its night dip of splendor. For a number of nights it made grim faces at us in its setting. A tantalizing mist, drawn as a curtain over the northern sea at midnight, had afforded curious advantages for celestial staging. We were unable to determine sharply the advent of the midnight sun, but the colored cloud and haze into which it nightly sank produced a spectacular play which interested us immensely.
Sometimes the great luminary was drawn out into an egg-shaped elongation with horizontal lines of color drawn through it. I pictured it as some splendid fire-colored lantern flung from the window of Heaven. Again, it was pressed into a basin flaming with magical fires, burning behind a mystic curtain of opalescent frosts. Blue at other times, it appeared like a huge vase of luminous crystal, such as might be evoked by the weird genii of the Orient, from which it required very little imagination to see purple, violet, crimson and multi-colored flowers springing beauteously into the sky.