midnight
Come with papa . '' By eleven o'clock the camp was quiet . Roger prowled about the condenser a bit , covered the engine with canvas and then went to bed . It had been a hard day and none of the three men were wakened by the smell of sulphur dioxide that began to hang over the camp at midnight . The dawn wind blew most of it away , but when Gustav rose to get breakfast , he sniffed suspiciously and called Roger . They traced a leak in the lower tier . Half the charge had evaporated during the night .