THERAPEUTICS. The healing art. THERME. Hot bathe. THERMOMETER. An instrument for measuring the temperature of the air, as re. specter heat and cold, founded on the principle that the expansions of matter are proportional to the augmentations of the temperature. The invention of the thermometer has been ascribed to different authors : to Cornelius Drebbet of Alemaar, by his countrymen Baer laare and Muschenbroeck • to Father Paid, by his biographer Fulgenzio • to Galileo, by incenzio iriviani ; but Sanctum' o assumes the invention to himself, and his claim is fully admitted by Malpighi and Borelfi. The first form of this invention was the air thermome ter, consisting of a glass tube connected at one end with a large glass ball, and at the other end immersed in an open vessel or ter minating in a bell with a narrow bottom. The vessel was filled with a coloured liquor that would not easily freeze, as aquafortis tinged with a solution of vitriol or copperas. The ball at the top then moderately warmed, the air contained in it was in part expelled, and then the liquor pressed by the external air entered at the lower ball and rose to a certain height in the tube, according to the temperature. The air being found not so fit for with accuracy the variations of heat and cold according to this form of the thermometer, which was first adopted, alcohol, or spirit of wine, was used by the Florentine academy, enclosed in a very fine cylindrical glass tube, having a hollow ball at me end, and hermetically sealed at the other. To the
tube in applied a scale, divided from the mid dle into one hundred parts, upwards and downwards. As spirit of wine to capable of a very considerable degree of rarefaction and condensation by heat and cold, when the heat of the atmosphere increases the spirit dilates, and consequently rises in the tube ; and when the heat decreases the spirit descends. As inconveniences were found to attend each of these thermometers, as alio that of M. Rean mew, which was constructed in a similar man. ner, Mr. Fahrenheit first employed mercury for thiswhich has since been univer• sally The method of constructing his thermometer, of which a tion is here given, is as follows: a small ball is blown at the end of a glass tube, of an uniform width throughout The ball and ppeerrtt of the tube aretheo to be filled with o,uxannlver which has been previously boiled to expel the air, the open end of the tube then being hermeti cally sealed, a scale is constructed by taking the two fixed points, namely, for the freezing point and 212° for the boiling point, and dividing the intermediate space into equal parts, or