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".