Stock Number: 10392


For sale, a patented viscometer in its case. It is used to determine the viscosity of lubricating oils and other liquids. An Australian invention, it was granted UK patent in 1918.


6-7/8 inch (17 cm) wide case


c. 1920

Country of manufacture

UK and Ireland

Category: Physics & Chemistry


MICHELL’S PATENT VISCOMETER, English / Australian, c. 1920, signed on the lid including the UK patent number (117234). Contained in the 6-7/8″ (17 cm) wide fitted mahogany case is a hollow steel cylinder with hard rubber grip and lower weighted steel assembly with three tiny polished steel grasping “pads” arranged on a cup-like segment of a sphere. There is also a polished steel ball which mates to these pads, a 0 – 100° C. thermometer, and instruction sheet. The outfit is complete and in fine condition. To determine the viscosity of lubricating oils or other liquids, one places a couple of drops on the pads, and noting the temperature of the unit, presses the ball onto the pads, quickly inverts the assembly, and measures precisely the time required for the ball to drop free of the cup. That duration in seconds, divided by the constant of the instrument (engraved on its plaque), gives the true viscosity of the liquid in C.G.S. units. Patented in the UK in 1918, it is the invention of A.G.M. Michell of Melbourne.

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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 [email protected].

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