Magdeburg hemispheres

Date1840-1850

Inventory Number1998-1-1221

ClassificationMagdeburg Hemispheres

Subject

Maker Joseph M. Wightman 1812 - 1885

Cultural Region

Place of Origin

Dimensions39.5 x 17.5 x 17.5 cm (15 9/16 x 6 7/8 x 6 7/8 in.)

Material

DescriptionThe two hemispheres can be removed from the round base, which is used to display them. Once out of the base, they can be put on a vacuum pump. One of the hemispheres has a stopcock to control the flow of air going in and out of the set when joined together. The upper half has a handle and another can be fixed on the lower half when not fixed to the base (handle missing here).

In Collection(s)

Exhibit 2005--CHSI's Putnam Gallery

Signedinlay in base: WIGHTMAN

Curatorial RemarksOwing to Wightman's type of business, it is possible that this instrument was made by someone else (whether in America or England) and was only sold by Wightman.

FunctionMagdeburg hemispheres are used to demonstrate the strength of the atmosphere's air pressure. Once air has been removed from inside the two hemispheres, it become extremely difficult to separate them (handles were provided on the hemispheres to try this experiment). Otto von Guericke illustrated this point with a horse carriage on each side of the tiny hemispheres. When there is no air pressure from inside, the normal air pressure from the surrounding atmosphere pushes on the hemispheres, forcing them together.

A video demonstration of a set of Magdeburg spheres by the Fondazione Scienza e Tecnica in Florence is available on Youtube here.

ProvenanceMallinckrodt Chemical Laboratory, Harvard University; transferred to CHSI May 1948.