Thermometer, ca. 1760
Photo by Peter Harholdt, 2004
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Photo by Peter Harholdt, 2004

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The instrument is a tall glass tube filled with mercury, fastened to a metal plaque, and housed in a box or sheath of wood. The slender tube of mercury has a bulb or ball at its lower end. It is held by flat straps at top and bottom to a silvered brass plate or plaque. The surface of the plaque is engraved up both sides of the tube. Up the left side are regularly spaced bars and numbers. Up the right side are the following script notations: Just freezing, Temperate, Summer Heat, Blood Heat, Fever Heat, Spirits Boil, Water Boils. At the base of the tube, the plate is engraved with projecting rays or spokes. At the top, the name of the maker is engraved in script: Nairne London.

The instrument is housed in an open sheath or box, built of sheets of walnut 3/16-inch thick, dovetailed together. The back board or panel has rounded shoulders at its top and a flat disc that is pierced by a hanging hole. The front of the instrument is protected by a sheet of glass that covers it from top to bottom. The side walls of the box are rabbetted out near their front edges to receive the glass cover, and near the joint with the back to receive the brass sheet holding the tube of mercury.

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