meteorology-第28章

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also　dries　water；　and　thickens　things　by　turning　air　into　water。



（Solidifying；　as　we　have　said；　is　a　form　of　drying。）　Now　those



things　that　are　not　thickened　by　cold；　but　solidified；　belong　rather



to　water；　e。g。。　wine；　urine；　vinegar；　lye；　whey。　But　those　things　that



are　thickened　（not　by　evaporation　due　to　fire）　are　made　up　either　of



earth　or　of　water　and　air：　honey　of　earth；　while　oil　contains　air。



Milk　and　blood；　too；　are　made　up　of　both　water　and　earth；　though　earth



generally　predominates　in　them。　So；　too；　are　the　liquids　out　of



which　natron　and　salt　are　formed；　and　stones　are　also　formed　from　some



mixtures　of　this　kind。　Hence；　if　the　whey　has　not　been　separated；　it



burns　away　if　you　boil　it　over　a　fire。　But　the　earthy　element　in



milk　can　also　be　coagulated　by　the　help　of　fig…juice；　if　you　boil　it



in　a　certain　way　as　doctors　do　when　they　treat　it　with　fig…juice；



and　this　is　how　the　whey　and　the　cheese　are　commonly　separated。



Whey；　once　separated；　does　not　thicken；　as　the　milk　did；　but　boils



away　like　water。　Sometimes；　however；　there　is　little　or　no　cheese　in



milk；　and　such　milk　is　not　nutritive　and　is　more　like　water。　The



case　of　blood　is　similar：　cold　dries　and　so　solidifies　it。　Those　kinds



of　blood　that　do　not　solidify；　like　that　of　the　stag；　belong　rather　to



water　and　are　very　cold。　Hence　they　contain　no　fibres：　for　the



fibres　are　of　earth　and　solid；　and　blood　from　which　they　have　been



removed　does　not　solidify。　This　is　because　it　cannot　dry；　for　what



remains　is　water；　just　as　what　remains　of　milk　when　cheese　has　been



removed　is　water。　The　fact　that　diseased　blood　will　not　solidify　is



evidence　of　the　same　thing；　for　such　blood　is　of　the　nature　of　serum



and　that　is　phlegm　and　water；　the　nature　of　the　animal　having　failed



to　get　the　better　of　it　and　digest　it。



　　Some　of　these　bodies　are　soluble；　e。g。　natron；　some　insoluble；



e。g。　pottery：　of　the　latter；　some；　like　horn；　can　be　softened　by　heat；



others；　like　pottery　and　stone；　cannot。　The　reason　is　that　opposite



causes　have　opposite　effects：　consequently；　if　solidification　is　due



to　two　causes；　the　cold　and　the　dry；　solution　must　be　due　to　the　hot



and　the　moist；　that　is；　to　fire　and　to　water　（these　being



opposites）：　water　dissolving　what　was　solidified　by　fire　alone；　fire



what　was　solidified　by　cold　alone。　Consequently；　if　any　things



happen　to　be　solidified　by　the　action　of　both；　these　are　least　apt



to　be　soluble。　Such　a　case　we　find　where　things　have　been　heated　and



are　then　solidified　by　cold。　When　the　heat　in　leaving　them　has



caused　most　of　the　moisture　to　evaporate；　the　cold　so　compacts　these



bodies　together　again　as　to　leave　no　entrance　even　for　moisture。



Therefore　heat　does　not　dissolve　them　（for　it　only　dissolves　those



bodies　that　are　solidified　by　cold　alone）；　nor　does　water　（for　it　does



not　dissolve　what　cold　solidifies；　but　only　what　is　solidified　by



dry　heat）。　But　iron　is　melted　by　heat　and　solidified　by　cold。　Wood



consists　of　earth　and　air　and　is　therefore　combustible　but　cannot　be



melted　or　softened　by　heat。　（For　the　same　reason　it　floats　in



water…all　except　ebony。　This　does　not；　for　other　kinds　of　wood　contain



a　preponderance　of　air；　but　in　black　ebony　the　air　has　escaped　and



so　earth　preponderates　in　it。）　Pottery　consists　of　earth　alone　because



it　solidified　gradually　in　the　process　of　drying。　Water　cannot　get



into　it；　for　the　pores　were　only　large　enough　to　admit　of　vapour



escaping：　and　seeing　that　fire　solidified　it；　that　cannot　dissolve



it　either。



　　So　solidification　and　melting；　their　causes；　and　the　kinds　of



subjects　in　which　they　occur　have　been　described。







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　　All　this　makes　it　clear　that　bodies　are　formed　by　heat　and　cold



and　that　these　agents　operate　by　thickening　and　solidifying。　It　is



because　these　qualities　fashion　bodies　that　we　find　heat　in　all　of



them；　and　in　some　cold　in　so　far　as　heat　is　absent。　These　qualities；



then；　are　present　as　active；　and　the　moist　and　the　dry　as　passive；　and



consequently　all　four　are　found　in　mixed　bodies。　So　water　and　earth



are　the　constituents　of　homogeneous　bodies　both　in　plants　and　in



animals　and　of　metals　such　as　gold；　silver；　and　the　rest…water　and



earth　and　their　respective　exhalations　shut　up　in　the　compound　bodies；



as　we　have　explained　elsewhere。



　　All　these　mixed　bodies　are　distinguished　from　one　another；　firstly



by　the　qualities　special　to　the　various　senses；　that　is；　by　their



capacities　of　action。　（For　a　thing　is　white；　fragrant；　sonant；



sweet；　hot；　cold　in　virtue　of　a　power　of　acting　on　sense）。　Secondly　by



other　more　characteristic　affections　which　express　their　aptitude　to



be　affected：　I　mean；　for　instance；　the　aptitude　to　melt　or　solidify　or



bend　and　so　forth；　all　these　qualities；　like　moist　and　dry；　being



passive。　These　are　the　qualities　that　differentiate　bone；　flesh；



sinew；　wood；　bark；　stone　and　all　other　homogeneous　natural　bodies。　Let



us　begin　by　enumerating　these　qualities　expressing　the　aptitude　or



inaptitude　of　a　thing　to　be　affected　in　a　certain　way。　They　are　as



follows：　to　be　apt　or　inapt　to　solidify；　melt；　be　softened　by　heat；　be



softened　by　water；　bend；　break；　be　comminuted；　impressed；　moulded；



squeezed；　to　be　tractile　or　non…tractile；　malleable　or



non…malleable；　to　be　fissile　or　non…fissile；　apt　or　inapt　to　be　cut；



to　be　viscous　or　friable；　compressible　or　incompressible；



combustible　or　incombustible；　to　be　apt　or　inapt　to　give　off　fumes。



These　affections　differentiate　most　bodies　from　one　another。　Let　us　go



on　to　explain　the　nature　of　each　of　them。　We　have　already　given　a



general　account　of　that　which　is　apt　or　inapt　to　solidify　or　to



melt；　but　let　us　return　to　them　again　now。　Of　all　the　bodies　that



admit　of　solidification　and　hardening；　some　are　brought　into　this



state　by　heat；　others　by　cold。　Heat　does　this　by　drying　up　their



moisture；　cold　by　driving　out　their　heat。　Consequently　some　bodies　are



affected　in　this　way　by　defect　of　moisture；　some　by　defect　of　heat：



watery　bodies　by　defect　of　heat；　earthy　bodies　of　moisture。　Now



those　bodies　that　are　so　affected　by　defect　of　moisture　are



dissolved　by　water；　unless　like　pottery　they　have　so　contracted　that



their　pores　are　too　small　for　the　particles　of　water　to　enter。　All



those　bodies　in　which　this　is　not　the　case　are　dissolved　by　water；



e。g。　natron；　salt；　dry　mud。　Those　bodies　that　solidified　through



defect　of　heat　are　melted　by　heat；　e。g。　ice；　lead；　copper。　So　much　for



the　bodies　that　admit　of　solidification　and　of　melting；　and　those　that



do　not　admit　of　melting。



　　The　bodies　which　do　not　admit　of　solidification　are　those　which



contain　no　aqueous　moisture　and　are　not　watery；　but　in　which　heat



and　earth　preponderate；　like　honey　and　must　（for　these　are　in　a　sort



of　state　of　effervescence）；　and　those　which　do　possess　some　water



but　have　a　preponderance　of　air；　like　oil　and　quicksilver；　and　all



viscous　substances　such　as　pitch　and　birdlime。







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　　Those　bodies　admit　of　softening　which　are　not　（like　ice）　made　up



of　water；　but　in　which　earth　predominates。　All　their　moisture　must　not



have　left　them　（as　in　the　case　of　natron　and　salt）；　nor　must　the



relation　of　dry　to　moist　in　them　be　incongruous　（as　in　the　case　of



pottery）。　They　must　be　tractile　（without　admitting　water）　or　malleable



（without　consisting　of　water）；　and　the　agent　in　softening　them　is



fire。　Such　are　iron　and　horn。



　　Both　of　bodies　that　can　melt　and　of　bodies　that　cannot；　some　do



and　some　do　not　admit　of　softening　in　water。　Copper；　for　instance；



which　can　be　melted；　cannot　be　softened　in　water；　whereas　wool　and



earth　can　be　softened　in　water；　for　they　can　be　soaked。　（It　is　true



that　though　copper　can　be　melted　the　agent　in　its　c