James Watt explains how he devised his measuring instrument, used in surveys of canals.
Date: Published in 1820.
Publication: Edinburgh Philosophical Journal, Volume 2, Number 3, Page 121-125.
In this paper we get inside the mind of James Watt, as he describes one of the instruments he devised for measuring distances.
Used in surveys for canals, this instrument was made up of a telescope with an object glass and eye glass. Watt explains how the micrometer works using crosshairs on the eyeglass and rods.
Watt demonstrated his micrometer to friends at the time of invention, although he did not publish anything about it or patent it. He recounts the claim from a Mr Green in 1778 for the same invention. Watt decided not to pursue a legal case against Green, stating that he 'disliked paperwar' (page 123).
Watt continued to modify his micrometer using prisms, and donated it to Professor Anderson of Glasgow College. The inventor eventually lost interest in it as he moved on to other ideas.
Watt communicated this paper to fellow inventor David Brewster.