DEMONSTRATION SOUNDING TUBES, probably English, late 19th century. These four lacquered brass tubes are mounted on a mahogany base 13-1/4″ x 4″ (34 x 10 cm), the tallest standing 11-1/8″ above the base. Each has a wood plunger piston which, when withdrawn rapidly, produces a sound whose frequency depends on the length of the standing column. Complete and all original, in fine condition.
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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 firstname.lastname@example.org.