Astronomy and the Bible;

THECLOCKOFTHEUNIVERSE 217

miles;andonedegreewouldbe25,000dividedby360,
orabout 69 miles,attheequator. Northorsouthof
theequator,thecircleoftheearthbeingsmaller,the
degreeissmaller;so thathalfwayfromtheequator
tothepole,itwouldbeverynearly 49 miles;andat
thepole,itwouldbenothing. Onedegreeoflatitude
wouldbeslightlyover 69 miles,practicallyanywhere
theobservationmightbetaken.
The sun completes a revolution of the earth in
twenty-fourhours;henceitpasses over 360 degrees
inthistime. Inonehour,itpassesover 15 degrees;
andinfourminutes,overonedegree.
Toascertain theGreenwich time,the ship carries
a chronometer that hasbeen carefully rated before
starting;andoftentwoorthreechronometersarepro-
vided,toguardagainsttheriskoferror,foranerror
maybeveryserious. Anerrorof evenoneminute
mightleadtheshipfifteenmilesoutofitscourse. But
wewillsupposethatthechronometeris correct;that
istosay,itpointstotwelveo'clockwhenthesunison
themeridianatGreenwich. Thecaptainmakeshisob-
servationofthesunonthemeridianwhereheis;and
wewillsupposethatwhenhedoesthis,thechronometer
pointstothree hoursfifty-twominutes. Thisdiffer-
enceoftimemeansadifferenceinlongitudeoffifty-
eightdegrees. Knowingthelatitude,thecaptainturns
tohistable,andsees justhow manymilesthere are
inadegreeoflongitudeathislatitude. Ifhewishes
totranslatehiscourseintomiles,hecanreadilydoso.
Butifhewishesmerelytoknowhislocation,hehas
buttolookathischartfortheassigned latitudeand