Popular science monthly . to move inlonger the phe-nomenon of expansion under the inllueiiceof heat is produced. When the tcm])era-ture is raised still liigher, so that the solidmelts and becomes a licpiid, the moleculesmove in paths so very much greater thatthere is less common interference. Last-ly, when the licpiid is made to boil, manyof the molecules are actually thrown off,and strike against the walls of the en-closing vessel, so violent is their mo\T-ment. The pressure of steam or ol aii\confined gas, then, must be regarded as aplicnonienon due entirely to millions andniillid
Popular science monthly . to move inlonger the phe-nomenon of expansion under the inllueiiceof heat is produced. When the tcm])era-ture is raised still liigher, so that the solidmelts and becomes a licpiid, the moleculesmove in paths so very much greater thatthere is less common interference. Last-ly, when the licpiid is made to boil, manyof the molecules are actually thrown off,and strike against the walls of the en-closing vessel, so violent is their mo\T-ment. The pressure of steam or ol aii\confined gas, then, must be regarded as aplicnonienon due entirely to millions andniillidiis of blows struck b\ millions andmillions of in\isil)le intiniiesimal mole-cules. If a thimbleful of boiling waterwere magnified to the size of a cathedralthe steam within it might seem to agigantic eye like myriads of bullets shotin all directions. Hecause countlessInillcts strike the walls of this hugethimble not singh, but at once in ver\rapid succession the effect of stead\|)ressure is produced. A single finger taj). Water was easily pumped for irrigating purposes inEgypt by means of Mr. Shumans Sun Power Plant may not e\en move an open door. Abillion simultaneous finger taps will shutit—shut it, moreover, as if it had beenpressed by a hand. At what temperature the moleculeswill fiy off from a boiling liquid dependsentirely on the pressure to which thelicjuid is subjected. The atmosphereweighs down on all earthly things with apressure that amounts to about fifteen pounds to thescpiare inch atthele\elofthcsea. If wateris heated inthe open air atsea level theflying mole-cules must beable to over-c o m e thatpressure;otherwise thewater does notboil. The tem-jierature atw h i c h the ycan fly o(T atsea level, atwhich water,in other wordscan boil, istwo hundredand twehe degrees Fahrenheit. On thetop of a high mountain where theatmos-l^here jiresses down with less force bei-ausethere is less ot it, the molecules will llyoff much more readily than at the \c\q\of the sea, with
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1872
