Map Evidence Lab
Maps
Historical maps, projections, geographic evidence, scriptural cosmology, and institutional symbolism — with sources, uncertainty, and clear separation between artifact facts and interpretation.
Patent · 1893
Gleason Time-Chart Map — U.S. Patent 497,917
Alexander Gleason's 1893 mechanical time-chart apparatus. The circular diagram is a north-polar azimuthal representation used to indicate time and bearing on the invented device.
Primary sources
The archival scan of the 1892 map itself is hosted by the Boston Public Library / Norman B. Leventhal Map & Education Center on Digital Commonwealth. Evidence Pros links directly to the repository's master scan — the image is never redrawn, cleaned up, enhanced, or substituted.
1892 Gleason map — archival scan
ark:/50959/7h149v85z — Digital Commonwealth (permanent identifier)digitalcommonwealth.org/search/commonwealth:7h149v85z →
Repository: Boston Public Library, Leventhal Map Center. Use the archive's master TIFF / full-resolution JPEG. Follow the rights statement shown on the record page.
U.S. Patent No. 497,917 — full text and drawings
patents.google.com/patent/US497917A/en →NARA scan (RG-241, Kansas City) — PDF →
Original registrant: Alexander Gleason. Issued May 23, 1893.
What the patent records
- A mechanical apparatus that uses a flat circular map to indicate time-of-day and bearing.
- The circular map itself is a north-polar azimuthal representation — a documented projection with known distortion properties.
- A patent records an invention. It does not scientifically validate the world model illustrated on it, nor does it constitute an institutional Earth-shape claim by the patent office.
Projection notes
- Preserves
- Azimuths (bearings) from the center point.
- Distorts
- Area and shape increase strongly toward the outer edge; the southern hemisphere is stretched into a ring.
- Intended use
- Time-chart / bearing indication on the patented apparatus.
- Compared with
- A globe-derived north-polar azimuthal equidistant projection shares this mathematics; other historical projections differ.