An early theodolite

Cathy Linacre

Head of Reference Service (RICS)

This lovely picture of an early theodolite, a precision instrument used by surveyors for measuring angles in the horizontal and vertical planes, comes from Speculum Topographicum: or The Topographicall Dlasse (1611) by Arthur Hopton.

Book illustration

It was taken from the copy of the book held in the historic collection of the RICS Library.

The book includes designs for this early form of theodolite. Hopton was fully aware of the relationship between his design and that of an earlier one by Digges and explains the advantages of his 'glass' over the earlier instrument. The examples he then offers of its applications include range-finding and military surveying. RICS Library also has a copy of that earlier book, A Geometrical Practical Treatize named Pantometria by Leonard Digges, published in 1571.

Mapping and measurement were developing rapidly at this time, as European countries began to expand into the New World of America. One of the first tasks when county’s discovered ‘new’ lands was to map them in order to quantify them and claim ownership. Jamestown in Virginia had been first settled in 1607, four years before this book was published.

It’s also interesting to think of the book as being contemporary with the first performances of The Tempest and the publication of the Kings James Bible.

The book also contains a delightful sideways map of Britain! I love the reference to Scotland as “Scotia parts” bearing in mind the book was published just eight years after James VI of Scotland also became James I of England and before the Act of Union:

Book illustration

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