meteorology-第30章

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combustible；　stone；　ice　are　not。　Bodies　are　combustible　when　their



pores　are　such　as　to　admit　fire　and　their　longitudinal　pores　contain



moisture　weaker　than　fire。　If　they　have　no　moisture；　or　if；　as　in



ice　or　very　green　wood；　the　moisture　is　stronger　than　fire；　they　are



not　combustible。



　　Those　bodies　give　off　fumes　which　contain　moisture；　but　in　such　a



form　that　it　does　not　go　off　separately　in　vapour　when　they　are



exposed　to　fire。　For　vapour　is　a　moist　secretion　tending　to　the　nature



of　air　produced　from　a　liquid　by　the　agency　of　burning　heat。　Bodies



that　give　off　fumes　give　off　secretions　of　the　nature　of　air　by　the



lapse　of　time：　as　they　perish　away　they　dry　up　or　become　earth。　But



the　kind　of　secretion　we　are　concerned　with　now　differs　from　others　in



that　it　is　not　moist　nor　does　it　become　wind　（which　is　a　continuous



flow　of　air　in　a　given　direction）。　Fumes　are　common　secretion　of　dry



and　moist　together　caused　by　the　agency　of　burning　heat。　Hence　they　do



not　moisten　things　but　rather　colour　them。



　　The　fumes　of　a　woody　body　are　called　smoke。　（I　mean　to　include　bones



and　hair　and　everything　of　this　kind　in　the　same　class。　For　there　is



no　name　common　to　all　the　objects　that　I　mean；　but；　for　all　that；



these　things　are　all　in　the　same　class　by　analogy。　Compare　what



Empedocles　says：　They　are　one　and　the　same；　hair　and　leaves　and　the



thick　wings　of　birds　and　scales　that　grow　on　stout　limbs。）　The　fumes



of　fat　are　a　sooty　smoke　and　those　of　oily　substances　a　greasy



steam。　Oil　does　not　boil　away　or　thicken　by　evaporation　because　it



does　not　give　off　vapour　but　fumes。　Water　on　the　other　hand　does　not



give　off　fumes；　but　vapour。　Sweet　wine　does　give　off　fumes；　for　it



contains　fat　and　behaves　like　oil。　It　does　not　solidify　under　the



influence　of　cold　and　it　is　apt　to　burn。　Really　it　is　not　wine　at



all　in　spite　of　its　name：　for　it　does　not　taste　like　wine　and



consequently　does　not　inebriate　as　ordinary　wine　does。　It　contains　but



little　fumigable　stuff　and　consequently　is　inflammable。



　　All　bodies　are　combustible　that　dissolve　into　ashes；　and　all



bodies　do　this　that　solidify　under　the　influence　either　of　heat　or



of　both　heat　and　cold；　for　we　find　that　all　these　bodies　are



mastered　by　fire。　Of　stones　the　precious　stone　called　carbuncle　is



least　amenable　to　fire。



　　Of　combustible　bodies　some　are　inflammable　and　some　are　not；　and



some　of　the　former　are　reduced　to　coals。　Those　are　called



'inflammable'　which　produce　flame　and　those　which　do　not　are　called



'non…inflammable'。　Those　fumigable　bodies　that　are　not　liquid　are



inflammable；　but　pitch；　oil；　wax　are　inflammable　in　conjunction　with



other　bodies　rather　than　by　themselves。　Most　inflammable　are　those



bodies　that　give　off　smoke。　Of　bodies　of　this　kind　those　that



contain　more　earth　than　smoke　are　apt　to　be　reduced　to　coals。　Some



bodies　that　can　be　melted　are　not　inflammable；　e。g。　copper；　and　some



bodies　that　cannot　be　melted　are　inflammable；　e。g。　wood；　and　some



bodies　can　be　melted　and　are　also　inflammable；　e。g。　frankincense。



The　reason　is　that　wood　has　its　moisture　all　together　and　this　is



continuous　throughout　and　so　it　burns　up：　whereas　copper　has　it　in



each　part　but　not　continuous；　and　insufficient　in　quantity　to　give



rise　to　flame。　In　frankincense　it　is　disposed　in　both　of　these　ways。



Fumigable　bodies　are　inflammable　when　earth　predominates　in　them　and



they　are　consequently　such　as　to　be　unable　to　melt。　These　are



inflammable　because　they　are　dry　like　fire。　When　this　dry　comes　to



be　hot　there　is　fire。　This　is　why　flame　is　burning　smoke　or　dry



exhalation。　The　fumes　of　wood　are　smoke；　those　of　wax　and　frankincense



and　such…like；　and　pitch　and　whatever　contains　pitch　or　such…like



are　sooty　smoke；　while　the　fumes　of　oil　and　oily　substances　are　a



greasy　steam；　so　are　those　of　all　substances　which　are　not　at　all



combustible　by　themselves　because　there　is　too　little　of　the　dry　in



them　（the　dry　being　the　means　by　which　the　transition　to　fire　is



effected）；　but　burn　very　readily　in　conjunction　with　something　else。



（For　the　fat　is　just　the　conjunction　of　the　oily　with　the　dry。）　So



those　bodies　that　give　off　fumes；　like　oil　and　pitch；　belong　rather　to



the　moist；　but　those　that　burn　to　the　dry。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　10







　　Homogeneous　bodies　differ　to　touch…by　these　affections　and



differences；　as　we　have　said。　They　also　differ　in　respect　of　their



smell；　taste；　and　colour。



　　By　homogeneous　bodies　I　mean；　for　instance；　'metals'；　gold；



copper；　silver；　tin；　iron；　stone；　and　everything　else　of　this　kind　and



the　bodies　that　are　extracted　from　them；　also　the　substances　found



in　animals　and　plants；　for　instance；　flesh；　bones；　sinew；　skin；



viscera；　hair；　fibres；　veins　（these　are　the　elements　of　which　the



non…homogeneous　bodies　like　the　face；　a　hand；　a　foot；　and　everything



of　that　kind　are　made　up）；　and　in　plants；　wood；　bark；　leaves；　roots；



and　the　rest　like　them。



　　The　homogeneous　bodies；　it　is　true；　are　constituted　by　a　different



cause；　but　the　matter　of　which　they　are　composed　is　the　dry　and　the



moist；　that　is；　water　and　earth　（for　these　bodies　exhibit　those



qualities　most　clearly）。　The　agents　are　the　hot　and　the　cold；　for　they



constitute　and　make　concrete　the　homogeneous　bodies　out　of　earth　and



water　as　matter。　Let　us　consider；　then；　which　of　the　homogeneous



bodies　are　made　of　earth　and　which　of　water；　and　which　of　both。



　　Of　organized　bodies　some　are　liquid；　some　soft；　some　hard。　The



soft　and　the　hard　are　constituted　by　a　process　of　solidification；　as



we　have　already　explained。



　　Those　liquids　that　go　off　in　vapour　are　made　of　water；　those　that　do



not　are　either　of　the　nature　of　earth；　or　a　mixture　either　of　earth



and　water；　like　milk；　or　of　earth　and　air；　like　wood；　or　of　water



and　air；　like　oil。　Those　liquids　which　are　thickened　by　heat　are　a



mixture。　（Wine　is　a　liquid　which　raises　a　difficulty：　for　it　is　both



liable　to　evaporation　and　it　also　thickens；　for　instance　new　wine



does。　The　reason　is　that　the　word　'wine'　is　ambiguous　and　different



'wines'　behave　in　different　ways。　New　wine　is　more　earthy　than　old；



and　for　this　reason　it　is　more　apt　to　be　thickened　by　heat　and　less



apt　to　be　congealed　by　cold。　For　it　contains　much　heat　and　a　great



proportion　of　earth；　as　in　Arcadia；　where　it　is　so　dried　up　in　its



skins　by　the　smoke　that　you　scrape　it　to　drink。　If　all　wine　has　some



sediment　in　it　then　it　will　belong　to　earth　or　to　water　according　to



the　quantity　of　the　sediment　it　possesses。）　The　liquids　that　are



thickened　by　cold　are　of　the　nature　of　earth；　those　that　are　thickened



either　by　heat　or　by　cold　consist　of　more　than　one　element；　like　oil



and　honey；　and　'sweet　wine'。



　　Of　solid　bodies　those　that　have　been　solidified　by　cold　are　of



water；　e。g。　ice；　snow；　hail；　hoar…frost。　Those　solidified　by　heat



are　of　earth；　e。g。　pottery；　cheese；　natron；　salt。　Some　bodies　are



solidified　by　both　heat　and　cold。　Of　this　kind　are　those　solidified　by



refrigeration；　that　is　by　the　privation　both　of　heat　and　of　the



moisture　which　departs　with　the　heat。　For　salt　and　the　bodies　that　are



purely　of　earth　solidify　by　the　privation　of　moisture　only；　ice　by



that　of　heat　only；　these　bodies　by　that　of　both。　So　both　the　active



qualities　and　both　kinds　of　matter　were　involved　in　the　process。　Of



these　bodies　those　from　which　all　the　moisture　has　gone　are　all　of



them　of　earth；　like　pottery　or　amber。　（For　amber；　also；　and　the　bodies



called　'tears'　are　formed　by　refrigeration；　like　myrrh；



frankincense；　gum。　Amber；　too；　appears　to　belong　to　this　class　of



things：　the　animals　enclosed　in　it　show　that　it　is　formed　by



solidification。　The　heat　is　driven　out　of　it　by　the　cold　of　the



river　and　causes　the　moisture　to　evaporate　with　it；　as　in　the