Page:South - the story of Shackleton's last expedition, 1914-1917.djvu/479

Rh Sea, with no knowledge of what was happening anywhere around us, forecasting was very difficult and at times impossible.

Great assistance in this direction was afforded by copies of Mr. R. C. Mossmann's researches and papers on Antarctic meteorology, which he kindly supplied to us.

I have tried to make this very brief account of the meteorological side of the Expedition rather more "popular" than scientific, since the publication and scientific discussion of the observations will be carried out elsewhere; but if, while showing the difficulties under which we had to work, it emphasizes the value of Antarctic Expeditions from a purely utilitarian point of view, and the need for further continuous research into the conditions obtaining in the immediate neighbourhood of the Pole, it will have achieved its object.

Owing to the continued drift of the ship with the ice, the programme of physical observations originally made out had to be considerably modified. It had been intended to set up recording magnetic instruments at the base, and to take a continuous series of records throughout the whole period of residence there, absolute measurements of the earth's horizontal magnetic force, of the dip and declination being taken at frequent intervals for purposes of calibration. With the ice continually drifting, and the possibility of the floe cracking at any time, it proved impracticable to set up the recording instruments, and the magnetic observations were confined to a series of absolute measurements taken whenever opportunity occurred. These measurements, owing to the drift of the ship, extend over a considerable distance, and give a chain of values along a line stretching, roughly from 77° S. lat. to 69° S. lat. This is not the place to give the actual results; it is quite enough to state that, as might have been expected from the position of the magnetic pole, the values obtained correspond to a comparatively low magnetic latitude, the value of the dip ranging from 63° to 68°.

So far as possible, continuous records of the electric potential gradient in the atmosphere were taken, a form of quadrant electrometer with a boom and ink recorder, made by the Cambridge Scientific Instrument Company, being employed. Here again, the somewhat peculiar conditions made work difficult, as the instrument was very susceptible to small changes of level, such as occurred from time to