The Atlantic Ocean enters the expedition not as a destination but as a vast, unseen ceiling: after mapping their underground route, the travelers realize that they have passed beneath the open sea. Its imagined waves overhead make the hidden geography of the journey newly tangible, while later calculations place the explorers beneath England and give their crossing an earthly scale.

The Ocean Above the Route

The expedition’s position becomes clear when Henry uses a map and compasses to check the direction and distance of their passage. His measurements show that the travelers are far beyond Cape Portland; continuing fifty leagues southeast would take them into the open sea. Professor Hardwigg receives the prospect with delight, while Henry voices the more unnerving implication: the Atlantic must flow above their heads.

The Professor treats the revelation as a straightforward geographical fact. He compares it to coal mines near Newcastle that extend far beneath the sea, making an underground route below ocean water seem no more extraordinary than known mining practice. Henry, by contrast, initially finds the idea unsettling. He reasons that the question is ultimately whether the granite roof is solid, whether the land lies overhead or the Atlantic’s billows do. As the passage continues southeast and descends, however, he grows accustomed to the thought of the sea above.

A Measured Position Beneath the Waves

The ocean’s presence becomes more than an alarming possibility when the Professor calculates the expedition’s position. After estimating that they have traveled 250 miles from their point of departure, Henry asks whether the mighty waves of the Atlantic are rolling over them. The Professor confirms it. Henry then imagines that storms may be raging above, with ships battling the blasts while the explorers continue unseen below.

The contrast enlarges the meaning of the underground passage: the surface world remains physically close, yet its weather and maritime dangers are separated from the travelers by the earth itself. The Atlantic is not directly seen from this route; its force in the narrative comes from the map-based deductions and the scale those deductions give to an otherwise hidden journey.

From Iceland to England

At the beginning of the expedition, the Atlantic is part of the ordinary geography around Iceland. Reykjavik lies beside Faxa Bay, where the ship Valkyrie is anchored; the bay is bordered to the north by the glacier of Sneffels. That surface setting establishes the point from which the travelers will descend beneath the island and eventually move toward the open sea below.

The explorers later cross the Central Sea on a raft. Before leaving the island where they have paused, Henry records their progress in his journal: they have traveled 270 leagues, more than 800 miles, on the inland sea, are 620 leagues from Iceland, and are exactly beneath England. This calculation connects their underground voyage to recognizable surface geography. The Atlantic first marks the transition from Iceland’s land beneath their feet to open water overhead; the later reckoning places the expedition’s extraordinary route under another named region of the surface world.