Gemini is guessing. It's actually: "hemisp[h]erium est saxeum vas curvatum infra per lineas designato .xii. diei horarum numero quas stili prominentis umbra cum transitu solis pretereundo distinguit et a priore ejus extremitate ad alteram usque stili umbram percurrit."
("hemisp[h]erium" and "stilus" in dark ink are labels.)
Google translation:
The hemisphere is a curved stone vessel with lines drawn below, marking the number of hours of the day which the shadow of the protruding stylus distinguishes as the sun passes by, and which runs from its first extremity to the other end of the stylus's shadow.
("hemisp[h]erium" and "stilus" in dark ink are labels.)
Google translation:
The hemisphere is a curved stone vessel with lines drawn below, marking the number of hours of the day which the shadow of the protruding stylus distinguishes as the sun passes by, and which runs from its first extremity to the other end of the stylus's shadow.

