Johnson's natural philosophy and key to philosophical charts : illustrated with 500 cuts; being reduced photographic copies of all the diagrams contained in the author's philosophical series of indestructible school charts ; for the use of schools and families (1878)
theirweight as equals the weight of theair displaced. Hence, if a bodyweighs less than an equal volumeof air, it will rise in the atmosphereuntil it meets with air of its owndensity. This is the principle uponwhich heated air, smoke, etc., rise. The buoyant effort of a balloonof a given size, Avill… … The balloon must not becompletely filled, otherwisethe expansion of the gas isliable to burst it, as thepressure of the atmospherediminishes. When the aeronaut wish-es to descend, he opens avalve by means of a cord,in the upper part of theballoon, to allow the gas toescape; to ascend, he throwsout…
Physics · Astronomy
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