From Southern Cross to

The turn of the twentieth century was a period of intense exploration and scientific activity on, and around the Antarctic continent. Most campaigns combined exploration and science in a comfortable alliance that produced results in both arenas. A core activity for most scientific programs was research into terrestrial magnetism, touted to be of mercantile interest (through the improvement of navigational charts) and intellectual inquiry (as the sources of the earth’s magnetic field were still a mystery). Douglas Mawson’s AAE (Aurora expedition 1911-14) represented the zenith of quality research in the field, especially in comparison to the modest beginnings during Borchgrevink’s Southern Cross expedition (1898-99).

In accord with the museum’s “Science and Collaboration” symposium theme, this presentation compares the work and practice of two journeys undertaken in the interests of geomagnetic science and notes the development of research in the discipline across some key expeditions between 1898 and 1914. It compares the work on sledge journeys of the Royal Geographic Society’s (Captain Scott’s) Discovery expedition (1901-04) and that of Mawson’s Australasian Antarctic Expedition (Aurora). Scott’s expedition was well funded, was sponsored by the Royal Society, had a custom-built ship as a floating magnetic observatory, had the most modern instruments and enjoyed a long preparation time. This paper investigates the elements that led to the conclusion that, although Mawson’s expedition did not enjoy all these key advantages, it produced superior results in the discipline of terrestrial magnetism. Improvements in quality of the Antarctic research into terrestrial magnetism through the so-called “Heroic Era” are explained.
Background to early research into terrestrial magnetism
There is a very long history of involvement in magnetic research by intellectuals and the Royal Navy in particular. For example Edmund Halley (Astronomer Royal and Captain R.N.) led two expeditions to the South Atlantic for magnetic science and produced a chart of the globe for the year 1700 showing lines of equal magnetic declination (isogons). A century later the polymath Alexander von Humboldt surveyed magnetism in Central and South America between 1799 and 1804, at more than one hundred locations and determined that magnetic intensity increased with increasing latitude on land, as well as at sea. He used a site in the Peruvian Andes as his reference station as it was on the magnetic equator (McConnell, 2005, p. 353). During the same years Matthew Flinders (Captain R.N, navigator and hydrographer) surveyed the coast of New Holland (Australia) and took thousands of observations including details of compass bearings, date, time, ship's heading, magnetic dip and geographic latitude and longitude. He noticed that the iron on board ship caused deviation and showed that swinging the ship around the points of the compass and recording the apparent declination on each heading could allow compensation to be made at sea (Gurney, 2004, p. 153; Mawer, 2006, p. 12). John Churchman (1753-1805) had also proposed this solution in 1796 (Jonkers, 2003, p. 169). On his return to England (after incarceration by the French) in 1812, Flinders proposed the Admiralty carry out a series of experiments related to deviation after which he devised a solution known as the “Flinders bar”, which was composed of soft iron and placed vertically and below the ship’s compass in the binnacle (Gurney, 2004, p. 171).

Alexander von Humboldt later joined the lobby agitating for the expansion of magnetic research in Britain and for James Clark Ross’s Antarctic expedition with it’s associated network of observatories. His influence in Britain shifted the focus of magnetic research away from the north magnetic pole and introduced a broader approach: “Consideration of the magnetic field as a cosmic phenomenon helped to broaden the subject and break down the barriers which the narrower interests of the Navy might have imposed” (Cawood, 1979).

“Intensity” represents the strength of the magnetic field of the earth. The total magnetic intensity may be calculated for any locality and time, then expressed as a single number by combining the vectors of horizontal and vertical intensity. Although determination of the direction of the vectors was possible, determination of the absolute field strength was not possible until the invention of the magnetometer by Gauss in 1832 (Jonkers, 2003, p. 26). Previously, relative field strength in the horizontal plane could be determined by the rate of oscillation of a compass needle but comparison was rarely valid as each needle had a unique magnetic signature.

It’s important to understand the distinction between the different types of observing and data collection during the period under consideration.

Firstly there was the routine of making observations at sea. James Clark Ross affirms the priority of the “at sea” magnetic observing program for the Erebus and Terror (1839-43) in the introduction to the account of his voyages to Antarctica:
We are not to expect from observations at sea the precision of which they are susceptible on land. Nonetheless, it has been ascertained that not only the Declination, but the Inclination and Intensity, can be observed, in moderate circumstances of weather and sea, with sufficient correctness, to afford most useful and valuable information, if patience be bestowed, and proper precautions adopted…it will be needless further to insist on the necessity of making a daily series of magnetic observations, in all the three particulars above-mentioned, whenever weather and sea will permit, an essential feature of the business of the voyage, in both ships. Magnetic observations at sea, will of course, be affected by the ship’s magnetism, and this must be eliminated to obtain results of any service.

(Ross, 1847, xxxiii)