Screw micrometer
Micrómetro de tornillo
- Date
- 1638-1640 · confidence high
- Place
- Salisbury, England
- Credited to
- William Gascoigne; the micrometer reticle of Auzout and Picard (1666)
- People
- 👤 Adrien Auzout1622–1691👤 Christiaan Huygens1629–1695👤 William Gascoigne1612–1644
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
A screw of known pitch that shifted threads at a telescope's focal point (Gascoigne) or measured diameters with a vernier, enabling angular and linear measurements to seconds of arc and hundredths of a unit. It introduced precision measurement into astronomy and mechanics.
Gascoigne died in 1644 without publishing; Auzout and Picard reinvented it in France in 1666, and Hooke and Towneley claimed English priority in 1667.
What it led to
- Precision positional astronomy (Flamsteed, Picard)
- The measurement of the meridian arc and the shape of the Earth
- Workshop metrology and interchangeable parts
Built on
Made possible
- Octant and sextant1731 (octante) / 1757 (sextante)
- Maudslay's 'Lord Chancellor' bench micrometerc. 1805
- Bench micrometer (Watt, 1772; Maudslay)
- Meridian (transit) telescope
- Micrometer calliper