seven in the evening
All day they journeyed through its savage interstices and struggled with its monstrosities of trap and sandstone . Twice they halted in narrow valleys , where a little loam had collected and a little moisture had been retained , affording meagre sustenance to some thin grass and scattered bushes . The animals browsed , but there was nothing for them to drink , and all began to suffer with thirst . It was seven in the evening , and the sun had already gone down behind the sullen barrier of a gigantic plateau , when they reached the mouth of the cañon which had once contained a river , and discovered by the merest accident that it still treasured a shallow pool of stagnant water . The fevered mules plunged in headlong and drank greedily ; the riders were perforce obliged to slake their thirst after them . There was a hastily eaten supper , and then came the only luxury or even comfort of the day , the sound and delicious sleep of great weariness . Repose , however , was not for all , inasmuch as Thurstane had reorganized his system of guard duty , and seven of the party had to stand sentry .