A text-book on chemistryFor the use of schools and colleges . IS AIR-THEEMOMETEHS. Fin. 11.. arranged tightly in the reservoir, but there is a free pas-sage for the air in and out of that part of the instru-ment. On touching the ball with the fingers, the airwithin it becomes warm, dilates, and depresses the li-quid in the tube; or, on touching with any cold body,it contracts, and the liquid rises. This form of thermometer is liable to a difficultywhich renders it impossible to relyupon its indications, except under par-ticular circumstances. It is affectedby variations of atmospheric pressure

- Image ID: 2AXH8RF
A text-book on chemistryFor the use of schools and colleges . IS AIR-THEEMOMETEHS. Fin. 11.. arranged tightly in the reservoir, but there is a free pas-sage for the air in and out of that part of the instru-ment. On touching the ball with the fingers, the airwithin it becomes warm, dilates, and depresses the li-quid in the tube; or, on touching with any cold body,it contracts, and the liquid rises. This form of thermometer is liable to a difficultywhich renders it impossible to relyupon its indications, except under par-ticular circumstances. It is affectedby variations of atmospheric pressure
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Image ID: 2AXH8RF
A text-book on chemistryFor the use of schools and colleges . IS AIR-THEEMOMETEHS. Fin. 11.. arranged tightly in the reservoir, but there is a free pas-sage for the air in and out of that part of the instru-ment. On touching the ball with the fingers, the airwithin it becomes warm, dilates, and depresses the li-quid in the tube; or, on touching with any cold body,it contracts, and the liquid rises. This form of thermometer is liable to a difficultywhich renders it impossible to relyupon its indications, except under par-ticular circumstances. It is affectedby variations of atmospheric pressure,as well as by changes of heat. Toprove that this is the case, place sucha thermometer under the receiver ofan air-pump, as shown in Fig. 11. Onproducing the slightest wpLisHdegree of rarefaction, theliquid in the tube is in-stantly depressed, and onrestoring the pressure of the air it returnsto its original position. This difficulty is avoided by a change inthe form of the instrument, by which at-mospheric pressure is altogether avoided.A tube, bent as in Fig. 12, has a bulbblown on eac

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