THE PLAIN QUADRANT, English, mid-18th century, made of finely-grained boxwood in the form of a quarter circle, 6″ (15 cm) in radius and 9/32″ (7mm) thick. The borders are ruled, and the arc is divided every degree from 0 to 90, with calibrations every 10° and intermediate 5° positions marked with triple-dot patterns. The quarter circle’s center is pierced with a hole for supporting a string and plumb bob (not present). Condition is very fine throughout. Sometimes referred to as a “mariner’s” or “plain” quadrant, this form is useful for simple measurement of solar or stellar altitudes. The angular altitude of the pole star, or the midday sun, leads directly to one’s latitude. The plain quadrant also can serve for simple inclination measurements, e.g., in construction, surveying, gunnery, etc.
Ask the Dealer
David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at [email protected]