A FINE DUTCH HOLLAND CIRCLE, 1757, signed in flowing script "J. v. Wyk, Amsterd., 1759." The 11-1/2" (29 cm) brass main plate is boldly divided with a circumferential degree scale, and set with four fixed sight vanes spaced 90° apart, and with a fine suspension mount for vertical use.
A rotating alidade has two tall (3-3/4") sight vanes, twin verniers reading to five arcminutes, and a compass engraved with degree scale and splendid rose marked with Dutch directionals. Main plate and alidade are both pierced with lovely arcuate shaping.
Each vane has both slit and pointer sights, in alternating order, designed for fore and back sighting. There is no longer any mounting bracket below, but four large screw heads could function as feet, for use on a plane table. Otherwise condition is fine, noting some darkening to the brass.
Here is a true Holland circle, designed to measure both vertical and horizontal angles and angular differences. Kiely finds the form described as early as 1612 (by Jan Dou). The present example was made by Jan (or his brother Jacobus) van Wyk (also Wijk), recorded by Rooseboom and by the Websters as maker of octants and surveying instruments, flourishing c. 1759 - 1785.
The Boerhaave, and the Utrecht University Museum, each has examples of physics demonstration apparatus by van Wyk. And Mörzer Bruyns, in his 2003 thesis on the octant, records seven surviving van Wyk octants (and see Tesseract Catalogue 29 Item 32). (8260)
OFFERED BY TESSERACT
David Coffeen, Ph.D,
New York 10706 USA