Sundials are usually designed for a specific location: the 'gnomon' that casts the shadow is set at the angle of latitude (how many degrees north of the equator) and the hour line angles are calculated to match. Sometimes a dial made for another latitude can be mounted to tell correct time at a new site.

Sundial for National Trust, Cragside, Northumberland

This dial for the National Trust at Cragside, the former home of Lord Armstrong, is engraved in gun metal, a form of bronze favoured by the Admiralty for making cannon (88% copper, 10% tin and 2% zinc).

The gnomon is in the form of the ‘trebuchet’ motif (a Roman war catapult) that Lord Armstrong designed for his personal use, the arm placed at the correct angle for telling local time.

Design for Armstrong sundial, National Trust, Cragside

The Latin tag composed especially for this dial reads FORTIS IN ARMIS, FORTIS IN HORTIS meaning ‘Strength in arms, strength in horticulture’.

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