372 
LIEUT. -GENERAL SABINE ON TERRESTRIAL MAGNETISM. 
“ The intensity lines in the southern regions rest on observations far too few to justify 
any sure reliance on their courses over a large part of their extent, and over the rest are 
altogether conjectural. Nevertheless there is good reason to believe in the existence 
and accessibility of two points of maximum intensity in the southern as in the northern 
hemisphere, the attainment of which would be highly interesting and important. A 
correct knowledge of the courses of these lines, especially when they approach their 
respective poles, is to be regarded as a first, and indeed indispensable preliminary step 
to the construction of a rigorous and complete theory of terrestrial magnetism.” 
Two ships, the ‘ Erebus’ and ‘ Terror,’ commanded respectively by Sir James Clark Ross 
and Captain Francis Rawdon Crozier, who, besides their other qualifications, were already 
favourably known for their magnetic observations in the course of several north polar 
voyages, were selected for this service. The magnetical instruments to be employed 
were prepared under my own direction, at an establishment then existing at Woolwich, 
but since transferred in part to the Physical Observatory at Kew. It was a most fortu- 
nate incident that instruments specially designed for the observation of the Dip and 
Intensity at sea had been devised a few years previously by Mr. Robert Were Fox, 
F.R.S., as with the instruments previously employed for these purposes the results 
would scarcely have been such as to have justified the undertaking. 
The ‘Erebus’ and ‘Terror’ sailed from the Thames in September 1839, arrived at the 
Cape of Good Hope in March 1840, and, after a sojourn of some days in Kerguelen 
Island, anchored at Hobarton in Tasmania, which was selected as one of the base- 
stations of the Survey, and where a Magnetic Observatory was established. Quitting 
Hobarton in November 1840, the two ships made good a nearly south course, surmount- 
ing the difficulties occasioned by the ice, and carefully observing the Magnetic Declina- 
tion, Dip, and Force in every twenty-four hours with very few exceptions, until, in the 
latitude of 70°, the discovery was made of the great Southern Continent of South Vic- 
toria ; and its coast was followed and examined until further progress towards the south 
was arrested, in a latitude little short of 80°, by a vast glacier extending in an east and 
west direction for about 30° of longitude. In returning to Hobarton on the approach 
of the southern winter, a route was chosen which led to the vicinity which had been 
named to Sir James Ross as the probable locality of a higher intensity than would be 
found in the region of the higher dips, and as the approximate locality of the second 
southern magnetic pole. The expedition arrived at Hobarton in April 1841, having 
completed the first year of the Survey, and having sustained no injury either to the ships 
or to the instruments. 
Quitting Hobarton in the following month (May 1841), it was Sir James Ross’s pur- 
pose to penetrate a second time to the southward in the largehnterval of longitude com- 
prised between the great glacier which had arrested their southern progress in the 
preceding year and the land named South Shetland, to the south of Cape Horn. This 
endeavour was frustrated by the ice, which admitted a progress through it between the 
