ten o'clock
The officer in command took careful note of the position and posted his sentries , taking care to be in communication with the pickets on his right and left , and the zereba in his rear . The sentries were double , that is , there were two men on each post , and were changed every hour . An hour 's sentry-go may seem to you but a short spell , but if you had a swarm of agile sharp-sighted savages prowling about you all the time , and knew that your own life and those of others who depended on you would be sacrificed if your vigilance flagged , perhaps you would find it long enough . It was ten o'clock when Kavanagh was roused to go on ; Dobbs was his companion , and Corporal Adams posted them . `` You are to challenge any one approximating this post , '' he said ; `` and if they say ` friend ' or ` rounds ' you must stop them and make them give the countersign . If they ca n't you must run them in , and if they wo n't be run in you must run them through with your bayonet ; if they wo n't be run through you must wait and see if there 's many of them , and if there is you must shoot . But you must n't alarm the camp without reason , mind you . ''