Description
A protractor is an instrument that measures angles. It can be semi-circular (180 degrees) or full circular (360 degrees).

What is special about this one is that the lower part beneath the semi-circular, which bears three bars that form two sections, allowing viewers to see through. This could be a later adaptation of Thomas Heath (1714-1757, possibly active time)'s product, which involves two smaller windows on the bottom of a protractor. The best presumption nowadays is that both collections are transversals, which are early models before the vernier scale was invented in 1631 and allowed people to measure in finer graduation and gain better accuracy.

The (possible) transversal manufactured by Thomas Heath is now in Science Museum Collection, obj. no. 1928-941, "semi-circular protractor 12-inch".

Charles and Richard Beilby were brothers. They were scientific instrument makers and owned a business in Bristol between 1808 and 1821, which was taken over by Thomas D. King and his father, John King, who were also scientific instrument makers.

Thomas Heath (1719-1773), English instrument maker. He was in the business in London with his apprentice and later partner Tycho Wing (1726-1773), and the brand was named Heath and Wing (1751-1773).
17/03/2023
Created by: Guey-Mei Hsu on 17/03/2023