A calm morning in June, the sky is clear and the north ablaze with the colours of sunrise—or is it sunset? The air is delicious, and a cool waft comes down the glacier. A deep ultramarine, shading up into a soft purple hue, blends in a colour-scheme with the lilac plateau. Two men crunch along in spiked boots over snow mounds and polished sastrugi to the harbour-ice. The sea to the north is glazed with freezing spicules, and over it sweep the petrels—our only living companions of the winter. It is all an inspiration; while hewing out chunks of ice and shovelling them away is the acute pleasure of movement, exercise.
The men measure out an area six feet by three feet, and take a preliminary temperature of the surface-ice by inserting a thermometer in a drilled hole. Then the ice begins to fly, and it is not long before they are down one foot. Nevertheless it would surprise those acquainted only with fresh water ice to find how tough, sticky and intractable is sea-ice. It is always well to work on a definite plan, channelling in various directions, and then removing the intervening lumps by a few rough sweeps of the pick. At a depth of one foot, another temperature is taken, and some large samples of the ice laid by for the examination of their crystalline structure. This is repeated at two feet, and so on, until the whole thickness is pierced to the sea-water beneath. At three feet brine may begin to trickle into the hole, and this increases in amount until the worker is in a puddle. The leakage takes place, if not along cracks, through capillary channels, which are everywhere present in sea-ice.
It is interesting to note the temperature gradually rise during the descent. At the surface the ice is chilled to the air-temperature, say -10 degrees F., and it rises in a steep gradient to approximately 28 degrees F.; close to the freezing-point of sea water. The sea-ice in the boat-harbour varied in thickness during the winter between five and seven feet.
In contrast with sea-ice, the ice of a glacier is a marvel of prismatic colour and glassy brilliance. This is more noticeable near the surface when the sun is shining. Deep down in a shaft, or in an ice-cavern, the sapphire reflection gives to the human face quite a ghastly pallor.
During the high winds it was always easy to dispose of the fragments of ice in the earlier stages of sinking a shaft. To be rid of them, all that was necessary was to throw a shovelful vertically upwards towards the lee-side of the hole, the wind then did the rest. Away the chips would scatter, tinkling over the surface of the glacier. Of course, when two men were at work, each took it in turns to go below, and the one above, to keep warm, would impatiently pace up and down. Nevertheless, so cold would he become at times that a heated colloquy would arise between them on the subject of working overtime. When the shaft had attained depth, both were kept busy. The man at the pit's mouth lowered a bucket on a rope to receive the ice and, in hauling it up, handicapped with clumsy mitts, he had to be careful not to drop it on his companion's head.
The structural composition of ice is a study in itself. To the cursory glance a piece of glacier-ice appears homogeneous, but when dissected in detail it is found to be formed of many crystalline, interlocking grains, ranging in size from a fraction of an inch to several inches in diameter. A grain-size of a half to one inch is perhaps commonest in Antarctic glacier-ice.
The history of Antarctic glacier-ice commences with the showers of snow that fall upon the plateau. The snow particles may be blown for hundreds of miles before they finally come to rest and consolidate. The consolidated snow is called neve, the grains of which are one-twenty-fifth to one hundredth of an inch in diameter, and, en masse, present a dazzling white appearance on account of the air spaces which occupy one-third to one-half of the whole. In time, under the influence of a heavy load of accumulated layers of neve, the grains run together and the air spaces are eliminated. The final result is clear, transparent ice, of a more or less sapphire-blue colour when seen in large blocks. It contains only occasional air-bubbles, and the size of the grains is much increased.
Lake-ice, freezing from the surface downwards, is built up of long parallel prisms, like the cells of a honey-comb on a large scale. In a lakelet near the Hut this was beautifully demonstrated. In some places cracks and fissures filled with snow-dust traversed the body of the ice, and in other places long strings of beaded air-bubbles had become entangled in the process of freezing. To lie down on the clear surface and gaze "through the looking-glass" to the rocky bottom, twenty feet below, was a glimpse into "Wonderland."
In the case of sea-ice, the simple prismatic structure is complicated owing to the presence of saline matter dissolved in the sea water. The saline tracts between the prisms produce a milky or opalescent appearance. The prisms are of fresh water ice, for in freezing the brine is rejected and forced to occupy the interstices of the prisms. Water of good drinking quality can be obtained by allowing sea water ice to thaw partially. The brine, of lower freezing-point, flows away, leaving only fresh water ice behind. In this way blocks of sea-ice exposed to the sun's rays are relieved of their salty constituents, and crumble into pellucid gravel when disturbed.
A popular subject commanding general interest, apart from the devoted attention of specialists, was zoological collecting. Seals and birds were made the prey of every one, and dredging through the sea-ice in winter and spring was always a possible diversion.