This unusual volvelle is a rare page from Kircher's "Mundus subterraneus, quo universae denique naturae divitiae", this being from the 1665 Amsterdam edition. According to the Latin sub-title the volvelle is a calculator for determining tides. This six inch volvelle is on the top half of a sheet of Latin text (9"x 15"). The base image consists of a circle with 24 Roman numerals, presumably representing the hours of the day. The first rotating paper piece is the Lunar Index and is numbered from 1 to 30 with a fixed arm extending outward with a crescent moon at its tip. The second and upper piece is the Solar Index (Index Solis) which also contains a pointer. At its center is a Polar-like hemispheric map with four large imaginative land masses surrounded by water and islands. The two movable pieces are fixed to the sheet with a sting at the center, both rotate freely. This is a very early working calculator. The sheet has the page number "154" in the upper left.

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Condition: A

The sheet has some light soiling and minor foxing.