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The Encyclopedia of Horology

Tool · Navicula dial

Navicula Dial

Partially verified

This brass navicula dial, inventory number 54358, represents an altitude sundial design known as the 'little ship of Venice'. The instrument measures 82 mm in width. The primary body is shaped like a vessel with a castellated poop and forecastle that integrate double pinhole sights. A central vertical mast functions as a suspension for an adjustable plumb-line, which is missing from this example. The dial is unsigned and its geographic origin remains unknown. The instrument features a rectilinear altitude sundial on the front, accompanied by a zodiac arc for seasonal adjustment. The back of the instrument carries a shadow-square with specific scales and an unequal hour quadrant for converting time readings. This piece is held by the Museum of the History of Science, Oxford.

The navicula dial viewed from the front, showing the central mast and ship-shaped body.
The navicula dial viewed from the front, showing the central mast and ship-shaped body. — Museum of the History of Science, Oxford. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
www.mhs.ox.ac.uk
Category
Tool · Navicula dial
Maker / attribution
Not established
Reference
Not recorded
Catalogue / lot identifier
54358
Source-reported date
15th century ?
Source-reported place
Not established

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

Construction and Design

The instrument is fashioned from brass and measures 82 mm across its widest point. Its design is based on the 'navicula' or 'little ship of Venice', which is a specific form of altitude dial. The body of the dial is engraved with hour-lines and shaped to resemble a ship, with castellated sections at either end representing the poop and forecastle. Each of these castellated ends contains a double pinhole sight to facilitate observations.

The vertical component, termed the mast, is fitted with a sliding suspension point. This mechanism was designed to hold a plumb-line, which is presently missing. A suspension hook is attached to the upper extremity of the mast, providing a means of holding the instrument upright during use.

Evidence for this section
  • “The main body, engraved with the hour-lines, is given the shape of a ship; in this case the sights are incorporated into a castellated 'poop' and 'forecastle'.”
  • “The 'mast' carries the suspension for a plumb-line , adjustable for date and latitude .”
  • “The castellated ship decks each incorporate double pinhole sights.”
  • “A suspension hook it attached to the top of the mast.”

Functionality and Scales

The front face displays a rectilinear altitude sundial with hour-lines marked for hours and half-hours. A zodiac arc featuring the names of various constellations is positioned below the hour-lines to allow for the adjustment of the mast angle relative to the date. There is an unmarked declination scale located to the side of the hour-lines intended for the positioning of a bead on the plumb-line.

The reverse side of the dial features a shadow-square with scales calibrated from 0 to 12 to 0. Additionally, an unequal hour quadrant is included on the back, allowing the user to convert time values obtained via the sundial into unequal or planetary hours.

Evidence for this section
  • “The front has a rectilinear altitude sundial, with one set of hour-lines marked twice, [0] to 12 and 12 to [0], with intermediate lines for half-hours.”
  • “A zodiac arc with the names of the constellations is beneath the hour-lines and serves to adjust the angle of the mast for the date.”
  • “The back has a shadow-square with scales on two sides 0 to 12 to 0, divided to 3, subdivided to 1, numbered by 1.”
  • “Also on the back is a unequal hour quadrant for converting time in equal hours found by the sundial into unequal or planetary hours.”

Attribution and Status

The navicula dial is an unsigned object with no specific attribution to a maker or a workshop. The period of manufacture is suggested as the 15th century, though this is marked with a question mark, and the geographical origin of the device is currently listed as unknown. The instrument is part of the collection held at the Museum of the History of Science in Oxford, recorded under the inventory number 54358.

Due to the lack of maker marks or historical context in the provided source, the dating remains purely speculative.

Evidence for this section
  • “Unsigned”
  • “15th century ?; origin unknown”
  • “Museum of the History of Science, Oxford”
  • “Inventory number 54358”

Open research questions

  • What material would have composed the missing plumb-line?
  • Can the specific configuration of the zodiac arc provide clues to the region of intended use?

Source evidence

Recorded claims and source quotations for Navicula Dial
FieldSource-reported valueSource quotation
MaterialBrass“Brass; 82 mm in width”
Inventory Number54358“Inventory number 54358”
Width82 mm“82 mm in width”
Latitude Scale20 to 65“adjustable against a scale of latitudes 20 to 65”
Shadow Square Scale0 to 12 to 0“shadow-square with scales on two sides 0 to 12 to 0”
Date Attribution15th century ?“15th century ?”
OriginUnknown“origin unknown”

Visible details

  • Main body engraved with hour-lines shaped like a ship
  • Castellated poop and forecastle with pinhole sights
  • Vertical mast with sliding suspension point
  • Shadow-square with numerical scales on the reverse

Research qualifications

  • The plumb-line is missing
  • The date is speculative and marked with a question mark
  • The place of manufacture is unknown

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

Navicula Dial

Reviewed 2026-10-26 · Record cdd4d984c6

Terms in this record

Glossary explanations for terms named in this object’s record.