Part 17 (1/2)
The observations made in the ”Absolute Hut”, carried out at frequent intervals and on each occasion occupying two men for several hours together, are necessary to obtain standard values as a check upon the graphic record of the self-recording instruments which run day and night in the ”Magnetograph House”.
But this is another story. Three hours, sitting writing figures in a temperature of -15 degrees F., is no joke. The magnetician is not so badly off, because he is moving about, though he often has to stop and warm his fingers, handling the cold metal.
The Magnetograph House had by far the most formidable name. The Hut, though it symbolized our all in all, sounded very insignificant unless it were repeated with just the right intonation. The Absolute Hut had a superadded dignity. The Hangar, in pa.s.sing, scarcely seemed to have a right to a capital H. The Transit House, on the and other hand, was the only dangerous rival to the first mentioned. But what's in a name?
If the Magnetograph House had been advertised, it would have been described as ”two minutes from the Hut.” This can easily be understood, for the magnetician after leaving home is speedily blown over a few hillocks and sastrugi, and, coming to an ice-flat about one hundred and fifty yards wide, swiftly slides over it, alighting at the snow-packed door of his house. The outside porch is just roomy enough for a man to slip off burberrys and crampons. The latter are full of steel spikes, and being capable of upsetting magnetic equilibrium, are left outside.
Walking in soft finnesko, the magnetician opens an inner door, to be at once accosted by darkness, made more intense after the white glare of the snow. His eyes grow accustomed to the blackness, and he gropes his way to a large box almost concealing the feeble glimmer of a lamp. The lamp is the source of the light, projected on to small mirrors attached to the magnetic needles of three variometers. A ray of light is reflected from the mirrors for several feet on to a slit, past which revolves sensitized photographic paper folded on a drum moving by clockwork. The slightest movements of the suspended needles are greatly magnified, and, when the paper is removed and developed in a dark-room, a series of intricate curves denoting declination, horizontal intensity and vertical force, are exquisitely traced. Every day the magnetician attends to the lamp and changes papers; also at prearranged times he tests his ”scale values” or takes a ”quick run.”
To obtain results as free as possible from the local attraction of the rocks in the neighbourhood, Webb resolved to take several sets of observations on the ice-sheet. In order to make the determinations it was necessary to excavate a cave in the glacier. This was done about three-quarters of a mile south of the Hut in working s.h.i.+fts of two men.
A fine cavern was hewn out, and there full sets of magnetic observations were taken under ideal conditions.
On sledging journeys the ”dip” and declination were both ascertained at many stations, around and up to within less than half a degree of the South Magnetic Pole.
While the wind rushed by at a maddening pace and stars flashed like jewels in a black sky, a glow of pale yellow light overspread the north-east horizon--the aurora. A rim of dark, stratus cloud was often visible below the light which brightened and diffused till it curved as a low arc across the sky. It was eerie to watch the contour of the arc break, die away into a delicate pallor and reillumine in a travelling riband. Soon a long ray, as from a searchlight, flashed above one end, and then a row of vertical streamers ran out from the arc, probing upwards into the outer darkness. The streamers waxed and waned, died away to be replaced and then faded into the starlight. The arc lost its radiance, divided in patchy fragments, and all was dark once more.
This would be repeated again in a few hours and irregularly throughout the night, but with scenic changes behind the great sombre pall of the sky. North-west, northeast, and south-east it would elusively appear in nebulous blotches, flitting about to end finally in long bright strands in the zenith, crossing the path of the ”milky way.”
By the observer, who wrote down his exact observations in the meteorological log, this was called a ”quiet night.”
At times the light was nimble, flinging itself about in rich waves, warming to dazzling yellow-green and rose. These were the nights when ”curtains” hung festooned in the heavens, alive, rippling, dancing to the lilt of lightning music. Up from the horizon they would mount, forming a vortex overhead, soundless within the silence of the ether.
A ”brilliant display,” we would say, and the observer would be kept busy following the track of the evanescent rays.
Powerless, one was in the spell of an all-enfolding wonder. The vast, solitary snow-land, cold-white under the sparkling star-gems; l.u.s.trous in the radiance of the southern lights; furrowed beneath the icy sweep of the wind. We had come to probe its mystery, we had hoped to reduce it to terms of science, but there was always the ”indefinable” which held aloof, yet riveted our souls.
The aurora was always with us, and almost without exception could be seen on a dark, driftless night. The nature of the aurora polaris has not yet been finally demonstrated, though it is generally agreed to be a discharge of electricity occurring in the upper, more rarefied atmosphere. The luminous phenomena are very similar to those seen when a current of electricity is pa.s.sed through a vacuum tube.
One receives a distinct impression of nearness, watching the s.h.i.+mmering edges of the ”curtains” in the zenith, but all measurements indicate that they never descend nearer than a few miles above the land-surface.
Careful records were taken to establish a relation between magnetic storms and aurorae, and a good deal of evidence was ama.s.sed to support the fact that auroral exhibitions correspond with periods of great magnetic disturbance. The displays in Adelie Land were found to be more active than those which occur in higher lat.i.tudes in the Ross Sea.
An occupation which helped to introduce variety in our life was the digging of ice-shafts. For the purpose of making observations upon its structure and temperature various excavations were made in the sea-ice, in the ice of the glacier, and in that of the freshwater lakes. The work was always popular. Even a whole day's labour with a pick and shovel at the bottom of an ice-hole never seemed laborious. It was all so novel.
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 gla.s.sy brilliance. This is more noticeable near the surface when the sun is s.h.i.+ning. 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 h.o.m.ogeneous, 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 ma.s.se, present a dazzling white appearance on account of the air s.p.a.ces which occupy one-third to one-half of the whole. In time, under the influence of a heavy load of acc.u.mulated layers of neve, the grains run together and the air s.p.a.ces 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.