2. The maker is probably Thomas Lorkin who is referred to in 1789 as taking on someone else's apprentice and in 1825 as making navigational instruments.
2. The formula given differ from, and are simpler than, those in "The sea-man's vade mecum of 1707".
http://www.bruzelius.info/Nautica/Rigging/Masting/Vademecum(1707)_p131.html
3. For example, on the rule the fore mast is given as 9/10 of the Main Mast. In the Vade Mecum the method takes account of the configuration of the deck but allows for it to be standing 1 yard below the main mast.
4. As the table includes reference to the gun deck, this was probably for naval ships.
5. For a diagram of a ship's mast click here.
This rule is from the collection of M Taylor.
Front view
Detail front left
Detail front right
Back view
Detail - back
