duringagreatpartoftheyear；theyextendtheircurrentsononesideatleastoftheequatorquitebeyondthemiddleofthecontinent，andevenuntilinAngolatheymeetthesea-breezefromtheAtlantic。
Ifthereaderrememberstheexplanationgivenatpage109，*
thatthecomparativewantofrainontheKalahariDesertiscausedbythemassofairlosingitshumidityasitpassesupandglidesoverthesubtendingridge，andwillturntothemap，hemayperceivethatthesamecauseisinoperationinanintensedegreebythemountainsofAbyssiniatorendertheregionaboutDarfurstillmorearid，andthattheflankingrangesmentionedliemuchnearertheequatorthanthosewhichrobtheKalahariofhumidity。
TheNile，evenwhilerunningthroughapartofthatregion，receivesremarkablyfewbranchesObservingalsothatthereisnoknownabruptlateralmountain-rangebetween6Degand12DegS。，butthatthereisanelevatedpartitionthere，andthatthesouthingandnorthingofthesoutheastersandnortheastersprobablycauseaconfluenceofthetwogreatatmosphericcurrents，hewillperceiveanaccumulationofhumidityontheflanksandcrownofthepartition，insteadof，aselsewhere，oppositetheKalahariandDarfur，adepositionoftheatmosphericmoistureontheeasternslopesofthesubtendingridgesThisexplanationisofferedwithalldeferencetothosewhohavemademeteorologytheirspecialstudy，andasahinttotravelerswhomayhaveopportunitytoexaminethesubjectmorefullyIoftenobserved，whileonaportionofthepartition，thattheairbynightwasgenerallyquitestill，butassoonasthesun’sraysbegantoshootacrosstheupperstrataoftheatmosphereintheearlymorning，acopiousdischargecamesuddenlydownfromtheaccumulatedclouds。
Italwaysremindedmeoftheexperimentofputtingarodintoasaturatedsolutionofacertainsalt，causinginstantcrystallization。