Astronomy and the Bible;

THEIMPRESSOFLIGHT 99

couldnolongercontain,notingenialshowersordif-

fuserain,butinterrifictorrents,ofwhichthedelug-

ingshowersofthetropics cangiveusonlyafeeble

conception; forthe drops fallingwithoutresistance,

wouldbe as destructive in their effectas volleys of

leadenshot."

—

JosiahP.Cooke, Ervingprofessorof
chemistryandmineralogyinHarvardUniversity.
Letustake anotherillustration. Agenerallawof
natureis,thatallsubstancesareexpandedbyheatand
contractedbycold. Water,exceptwithincertainvery
narrowlimits,tobe considered shortly, formno ex-
ceptiontothegeneralrule. In fact,butforthisex-
pansion, it would be difficultto heat or cool large
quantitiesofliquids.
"Allliquidsareverypoorconductorsofheat, and
can be heated only by bringing their particles suc-
cessively incontact withthesource ofheat. When
youset ateakettleover afire, thefirsteffectofthe
heatistoexpandtheparticlesofwaterrestingonthe
bottomofthekettle, which,beingthusrenderedspe-
cificallylighter,rise,andaresucceededbycolderpar-
ticles,whichareheatedandriseintheirturn;andthus
thecirculationisestablishedbywhichalltheparticles
are successively brought in contact withthe heated
bottom ofthe kettle, and inthe course of time the
temperatureofthewholemassisraisedtotheboiling
point.
"Thecaseis similarwhen youaddicetoapitcher
ofwaterinordertocool it. Thewateratthetopof
thepitcher,incontactwiththeice,is,ofcourse,cooled,
andbeingrenderedspecificallyheavierthanthewater