202 ASTRONOMYANDTHEBIBLE
summerwinds,each bunch ofgrassin thepastures,
everycornstalkthatrustlesontheprairies,theshrub
that ornaments the landscape, and every giant tree
that wrestles with the wind,—these all show some-
thingofthestupendouspowermanifestedbythevege-
tablekingdom.
Butletusnextconsiderthetidesofpowerflowing
downupontheearthinthegenialraysofthesummer
sun. According to recentmeasurements, it appears
thatoneverysquare yardoftheearth'ssurface ex-
posedperpendicularlytothesun'srays,intheabsence
of anabsorbing atmosphere, therecouldbe derived
morethanonehorsepower, iftheheatwereallcon-
vertedtothisuse. Attheequator,asteamercouldbe
drivenata fair rateof speed, byutiHzing onlythe
sunshinethatbeatsdownuponitsdecks. Onsosmall
anareaasManhattanIsland, orthatoccupiedbythe
cityofLondon,thenoontideheatis enough,couldit
allbeappliedthus,todriveallthesteamenginesinthe
world. Thusweseethatmillionsofhorsepower,un-
measuredbyman,areraineddownuponusintheform
ofsunlight. Ifwewereabletogatherupthisenergy
insomewayandstoreitforuse,daylightalonewould
furnishaninexhaustiblesupplyofpower.
Thesun,besidessupplyinguswithlightandheat,
keepstheearthalwaysnearitbythe forceofgravi-
tation. Seldom dowe thinkofthemightypullitis
alwaysexertinguponthisearth. It reachesoutalso
tolayholduponworldsmuchlargerthanours,much
fartherawayintheconfinesofspace,andthattravel
inmuchvasterorbits;andthesetooitholdsinanun-