18th Century Forged Iron Drafting Compass

Small 18th century compass divider found at Willowbrook.


This is an 18th century forged iron blacksmith made drafting compass, found in the yard at Willowbrook/Byrnside’s Fort.

This may have been used in construction of the fort.

Dividers and compasses are drawing instruments that have been used since antiquity to measure distances, transfer lengths from one drawing to another, and draw circles. The Greek mathematician, Euclid, limited the constructions in his Elements of Geometry to those that could be done with an unmarked straight edge and rudimentary compass. Ancient Roman dividers survive in the collections of the British Museum. Before the 18th century, when one leg was modified to take a pen or pencil point, compasses had two sharp points, like dividers. The user scratched the writing surface in the shape of a circle and then inked the scratches.

If you have used your thumb and forefinger to compare a distance between two points on a map with the mileage scale in the map’s legend box, then you have used your body as a pair of dividers. This instrument typically has two legs, hinged at one end and with sharp points at the other end. It can be used by itself or in combination with a calculating instrument, such as a sector.

Most Americans probably last held a drawing compass in elementary school. It also usually has two legs, one with a sharp point for holding the instrument in place and one with a pen or pencil point for tracing out a circle. Some compasses have interchangeable points, so that they can also function as dividers. Both types of objects were widely sold individually or in sets of drawing instruments from the 17th through the 20th centuries. Instrument makers, such as Nicolas Bion in the 18th century and William Ford Stanley in the 19th century, provided detailed descriptions of the different types of dividers and compasses suitable for different drawing tasks. By the 20th century, manufacturers and retailers devoted considerable space in their catalogs to these instruments.

Mount Vernon has a small one carried by George Washington:

Lacking formal training as a draftsman or architect, George Washington developed his skills through practice and by consulting printed manuals. Though few of his rendered drawings survive, those that do show his exacting concern for detail. This set of pocket drawing instruments may have been used by Washington to create the initial design for a new structure or landscape feature at Mount Vernon while he was taking the lay of the land. It features a divider, pencil, and drawing scale in its compact red morocco leather case.


W-2806/B; Part of the pocket drawing set; Copper-alloy and iron single-hand divider


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