about midnight
We could endure for that length of time without much difficulty or hardship , after which , I ventured to hope , our anxiety respecting the savages would be at an end . I relieved Julius as guard , and sent him to the inner cavern to get some food and a few hours ' sleep prior to relieving me in turn . I fondly believed that the existence of our cavern was unknown , and that we had been fortunate enough to replenish our stock of water unobserved ; but I afterward had reason to suspect the contrary . I maintained a keen watch at the mouth of the cavern until about midnight , my estimate of the time being based upon the position and posture of the Southern Cross in the sky -- that constellation being visible from the mouth of the cavern -- when Mrs Vansittart came stealing out to me with the whispered enquiry as to whether I was not tired enough to require a relief . As a matter of fact I was , and did not hesitate to say so , since the night was quiet , I had seen nothing of a suspicious character , and Julius had had a good long rest . The lady retired , and presently Julius came along , gaping and yawning , and stretched himself out beside me . I remained with him , conversing in low whispers , for about ten minutes , until I was satisfied that he was broad awake , and then , with a final word of caution , I left him and retreated to my own couch , where I soon fell asleep .