the secret mechanism

The secret mechanism is the hidden device that controls access to the finis Africae, the most forbidden chamber of the abbey's library. It is a concealed latch built into the carved letters of the apocalyptic verse "Super thronos viginti quatuor" above the mirror in the south tower, requiring the user to press the first and seventh letters of the word "quatuor"—the 'q' and the 'r'—to open the mirror as a door. This mechanism is the physical key to the library's ultimate secret, the hiding place of Aristotle's lost second book of the Poetics, and its discovery by William of Baskerville and Adso of Melk on the sixth night of their investigation leads directly to the final confrontation with Jorge of Burgos and the destruction of the library.

Design and Location

The mechanism is integrated into the architecture of the library labyrinth, specifically in the room of the south tower whose scroll reads "Super thronos viginti quatuor." This room contains a large mirror that distorts reflections, a device intended to frighten intruders. The letters of the verse are carved or incised into the wall, and those of the word "quatuor" are metal outlines connected to a hidden mechanism. When the 'q' and the 'r' are pressed, they produce a sharp click, and the entire frame of the mirror shudders, causing the glass surface to snap back. The mirror is a door hinged on its left side, which opens outward to reveal the entrance to the finis Africae. The mechanism is walled up behind the letters, making it inaccessible from the outside.

Discovery and Operation

William deduces the secret of the mechanism on the sixth night, after Adso's chance remark about Salvatore's Latin phrase "tertius equi" (the third letter of the word "equus" is 'u') triggers a realization about the material supposition of words. William re-reads Venantius's coded message, "primum et septimum de quatuor," and understands that it refers not to the first and seventh of four things, but to the first and seventh letters of the word "four" itself—the 'q' and the 'r' in "quatuor." He and Adso rush to the mirror room, where William, standing on tiptoe, presses the 'q' and then the 'r', causing the mirror to open. They enter the finis Africae, where Jorge of Burgos is waiting for them.

Narrative Significance

The secret mechanism is the final puzzle that William must solve to reach the heart of the mystery. Its discovery confirms that the series of murders was driven by the desire to protect the forbidden book hidden in the finis Africae. The mechanism also serves as a trap: Jorge, knowing the abbot would try to enter through a different passage, breaks the rope controlling the counterweights, sealing the abbot in the secret stairway to die. The mechanism thus becomes the instrument of the abbot's death and the gateway to the novel's climactic confrontation, where Jorge devours the book and inadvertently starts the fire that destroys the library.