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A text-book on chemistryFor the use of schools and colleges . rated inFig. 230. The fruits are placedin a jar, closed by a soundcork covered with sealing-wax. A small hole is madethrough the cork, and the airexhausted. When the vacu-um is as complete as may be,the hole is closed by meltingthe wax in a converging beamof sunlight. On the largescale, the things to be pre-served are inclosed in tin cans, which are sealed by sol-dering, except a pinhole that is left through the cover.The tins are immersed in boiling water, and when steamissues from the pin-hole it is closed by a drop of meltedsolde

A text-book on chemistryFor the use of schools and colleges . rated inFig. 230. The fruits are placedin a jar, closed by a soundcork covered with sealing-wax. A small hole is madethrough the cork, and the airexhausted. When the vacu-um is as complete as may be,the hole is closed by meltingthe wax in a converging beamof sunlight. On the largescale, the things to be pre-served are inclosed in tin cans, which are sealed by sol-dering, except a pinhole that is left through the cover.The tins are immersed in boiling water, and when steamissues from the pin-hole it is closed by a drop of meltedsolde Stock Photo
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The Reading Room / Alamy Stock Photo

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2AXFE59

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1520 x 1643 px | 25.7 x 27.8 cm | 10.1 x 11 inches | 150dpi

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A text-book on chemistryFor the use of schools and colleges . rated inFig. 230. The fruits are placedin a jar, closed by a soundcork covered with sealing-wax. A small hole is madethrough the cork, and the airexhausted. When the vacu-um is as complete as may be,the hole is closed by meltingthe wax in a converging beamof sunlight. On the largescale, the things to be pre-served are inclosed in tin cans, which are sealed by sol-dering, except a pinhole that is left through the cover.The tins are immersed in boiling water, and when steamissues from the pin-hole it is closed by a drop of meltedsolder. From the foregoing experiments and considerations,it is demonstrated that the prime fact in pneumatics is,that air has weight; from this arise its pressure andvarying density at different altitudes. Its elastic forcemust also be equal to the pressure upon it; if it wereless, the air would compress ; if greater, dilate. How may the necessity of air to combustion be shown? Howmay meats, etc., be preserved? What facts in pneumatics have wedemonstrated ? ?. THE BAROMETER. 253 LECTURE XLV. Atmospheric Air.— Construction of the Barometer.—Cause of its Phenomena.—History of its Inventionby Torricelli. — JPascaVs Experiment. — Illustrationsof the Nature of Pressure.—Variability of Pressure.—Disturbances in the Composition of the Air.—Arecorrected by the Winds and Diffusion.—Illustrationsof Diffusion.—The Air is a Mixture. — MarriottsLaw. If we take a tube of glass, a 5, Fig. 231, more than30 inches long, sealed at one end and open at the m 231other, and, having filled it with quicksilver, in-vert it in a cup of that metal, c, the mercurywill not flow out of the tube, but will remainsuspended at a height of from 28 to 30 inches,a vacuous space being left at the upper part. Ascale, dj divided into inches and decimal parts,the zero being at the level of the mercury in thecup, completes the instrument. It is termed abarometer. The cause of the suspension of the mer