10 o'clock
He went to the bottom of a deep shell crater , and , lying upon his stomach , he took a scrap of map from under his shirt and spread it below him . He took a tiny electric torch from his pocket and illumined the sheet dimly . A series of squares , into which that sector was divided , marked his path for the front -- each square of the series numbered in ink and designated by a time , such as 32 , 24 , 19 , 16 , 10 and so , forth . They told the moment before 10 o'clock , at which , upon the square marked , the French fire would cease , not to start again until the fire ceased , at the next lowest minute , upon the next square . Down to five minutes to 10 o'clock they showed the safe path , after that friend and foe alike on this side of the German lines must shift for themselves . Chester 's mind caught the pattern of the next numbered square ; he repeated to himself the time intervals . He climbed up out of the shell hole and swiftly passed the next square as the shells began falling behind him .