The Cape of Good Hope (Africa) or the Cape of Horn (South America). In other words,
Walton expects, that, once cutting across the Arctic Ocean he should discover a northern
passage into the Pacific Ocean through the Bering Sea, the change of seasons might
make it impossible for him to reverse course and return to England across the top
of Siberia and Scandinavia. Thus, it might be necessary for him to traverse the Southern
Hemisphere on his return.