Page:Evolution of the thermometer.djvu/51

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EVOLUTION OF THE THERMOMETER.

ise on chemistry (1669), mentions the thermometer as a well-known instrument, and Gabriel Clauder in the "Miscellanea curiosa Acad. nat. curiosa" (Dec. 2, Anno 6, p. 351, 1687), describes a "thermoscopium noviter inventum " adapted to immersion in liquids.

There was published at Amsterdam, in 1688, an illustrated work entirely devoted to barometers, thermometers, and hygrometers, written by Dalencé, who concealed his name under the initial D——. I have already referred to this interesting book in connection with the Drebbel myth, but it deserves emphasizing, for it contains an imperfect summary of thermometrical knowledge up to that date; to avoid repetition, however, I shall only notice items not previously given here.

Dalencé describes the Italian thermoscope as having a bulb the size of a pigeon egg and a tube as big as a quill pen; he suggests the use of a mixture of three parts of water with one of aqua fortis to prevent the liquid freezing, and a flattened bulb to permit heat, or cold, more readily to penetrate the centre of the liquid. He proposed, also, that two points should be marked on the scale, the freezing-point of water, to be marked "cold," and the