midnight
It might seem strange for anyone to sleep aboard a moving airship , but , the truth of the matter was , that our friends were realty worn out with nervous exhaustion . They had tired themselves out , not only physically , but mentally , and sleep was really forced on them . Otherwise they might not have slumbered at all . It was shortly past midnight when Dick , who , in spite of his attempts to keep awake , had partly dozed off , was suddenly aroused by a howl from Grit . `` What -- what 's the matter , old boy ? '' he asked . `` In trouble again ? ''