the lodestone

The lodestone is a magnetic stone that appears in Severinus of Sankt Wendel's infirmary, where William of Baskerville demonstrates its power to attract iron. It later becomes the conceptual basis for William's plan to navigate the library labyrinth by constructing a magnetic compass, though the plan is never executed.

Discovery and Demonstration

During the second day, while examining Venantius of Salvemec's corpse in Severinus's laboratory, William notices a stone lying on a shelf. When Severinus asks whether he knows it, William replies that he does, but not as a medicine. He takes a little knife from his habit and slowly holds it toward the stone. As the knife approaches, the blade makes an abrupt movement, sticking to the stone with a faint metallic sound, even though William's wrist remains absolutely still. William explains to Adso that the stone attracts iron. Severinus, who had received the stone some time ago, admits he has not yet discovered its therapeutic virtues.

Theoretical Application: The Magnetic Compass

On the fifth day, after the discovery of Berengar of Arundel's body and the loss of William's lenses, William and Adso discuss how to orient themselves in the library labyrinth. William proposes using a machine that tells them where north is, even indoors and at night, without needing the sun or stars. He explains that such a machine has been constructed and used by navigators, exploiting the power of the lodestone. He describes the method of the Arab scholar Baylek al-Qabayaki: take a vessel filled with water, set afloat a cork with an iron needle stuck into it, then pass the magnetic stone over the surface until the needle acquires the same properties. The needle will then turn and point north, and if the vessel is marked with the cardinal directions, one can always know which way to turn to reach the east tower.

Practical Abandonment

Despite the theoretical elegance of the plan, William never constructs the compass. When Adso excitedly suggests fetching Severinus's stone, a vessel, water, and a cork, William hesitates. He admits that he has never seen a machine that, however perfect in the philosophers' description, is perfect in its mechanical functioning, whereas a peasant's billhook, which no philosopher has ever described, always functions as it should. He also worries about the impracticality of wandering through the labyrinth with a lamp in one hand and a vessel full of water in the other. Instead, William uses the mathematical principles suggested by the compass idea to deduce the library's layout from the outside, creating a map that allows them to navigate without the device.

Narrative Significance

The lodestone serves as a symbol of William's intellectual method: a natural phenomenon that, when understood, can be harnessed to solve practical problems. Its failure to be deployed in practice mirrors the larger theme of the novel, where rational deduction repeatedly encounters the messy, unpredictable reality of human action and material contingency. The stone also connects William to the tradition of Roger Bacon and the natural magic that seeks to understand and manipulate the physical world for human benefit, a tradition that stands in opposition to the library's ethos of concealment and prohibition.