Walton refers to previous explorers of the northern wilderness. Sir John Ross, in
the Introduction to his Narrative of a Second Voyage in Search of a north-west passage
and of a residence in the Arctic Regions during the years 1829, 1830, 1831, 1832,
and 1833 (London: Webster, 1835), pp. i-xxiv provides a useful, near-contemporary
history of such expeditions.