October 13, the day when the mast blew down, was known in wireless circles as Black Sunday. All had worked keenly to make the "wireless" a success, and the final event was considered to be a public misfortune. However, the honours were to be retrieved during the following year.
It fell to the lot of most of the Staff that they developed an interest in terrestrial magnetism. For one thing every man had carried boulders to the great stockade surrounding the Magnetograph House. Then, too, recorders were regularly needed to assist the magnetician in the absolute Hut. There, if the temperature were not too low and the observations not too lengthy, the recorder stepped out into the blizzard with the conviction that he had learned something of value, and, when he sat down to dinner that night, it was with a genial sense of his own altruism. In his diary he would write it all up for his own edification.
It would be on this wise: The Earth's magnetic force, which is the active agent in maintaining the compass-needle in the magnetic meridian** at any particular spot, acts, not as is popularly supposed, in a horizontal plane, but at a certain angle of inclination with the Earth's surface. The nearer the magnetic poles the more nearly vertical does the freely suspended needle become. At the South Magnetic Pole it assumes a vertical position with the south end downwards; at the North Magnetic Pole it stands on its other end. At the intermediate positions near the equator the whole force is exerted, swinging the needle in the horizontal plane, and in such regions ordinary ships' compasses pivoted to move freely only in a horizontal plane give the greatest satisfaction. On approaching the magnetic poles, compasses become sluggish, for the horizontal deflecting force falls off rapidly. The force, acting in a vertical direction, tending to make the needle dip, correspondingly increases, but is of no value for navigation purposes. However, in the scientific discussion of terrestrial magnetism, both the horizontal and vertical components as well as the absolute value of the total force are important, and the determination of these "elements" is the work of the magnetician. Affecting the average values of the "magnetic elements" at any one spot on the Earth's surface are regular diurnal oscillations, apparent only by the application of very delicate methods of observation: also there are sudden large irregular movements referred to as magnetic storms; the latter are always specially noticeable when unusually bright auroral phenomena are in progress.
** The magnetic meridian is the straight line joining the North
and South Magnetic Poles and passing through the spot in question.
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 passing, 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 shifts 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.