GRAVITY OF ATMOSPHERIC AIR.

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will burst the bladder with a loud report. In a similar situationa thin plate of glass may be broken.

Experiment X.

If a glass bulb with a long neck filled with water be put in-verted into a vessel of the same fluid, placed under a receiver,and tire latter be exhausted, on re-admitting the air its pressureupon the surface of the water in the vessel, will cause the fluidto rise up in the bulb.

Experiment XI.

If on a plate, called a transferrer, the air be exhausted froma long receiver, and then water be admitted through a pipeby means of a stop-cock, die water will be pressed up and forma fountain.

Experiment XII.

If die air be exhausted from a vessel and by means of a cockkept so, and the vessel be weighed while it is empty, and againweighed when die air is re-admitted; the difference will be theweight of the quantity of air the vessel contains.

Experiment XIII.

Fill a glass tube, about three feet long, and closed at one end,widi mercury; then insert the open end in a cup or vessel of thesame fluid. The mercury in the tube will be kept suspended,by the pressure of the external air on die surface of that whichis on the open cup: when this pressure is removed by placingdiem under a receiver, and exhausting it; the mercury in thetube will sink, and rise again on re-admitting the air.

On the gravity of the air depends the ascent of w r ater in pumps,syphons, &c. and the phenomena of the barometer.