five o'clock
If this ascension proved a success the French government would receive the balloon and the secret of the steering and propelling gear , along with the formula for the silvery dust used to inflate it . Even she understood what a terrible engine of war such an aërial ship might be , from which two men could blow up fortress after fortress and city after city when and where they chose . Armies could be annihilated , granite and steel would be as tinder before a bomb or torpedo of picric acid dropped from the clouds . On the 10th of August , a little after five o'clock , Jack left Lorraine on the terrace at Morteyn to try once more to see the marquis -- for Lorraine 's sake . He turned to the west , where the last Uhlan of the rear-guard was disappearing over the brow of the hill , brandishing his pennoned lance-tip in the late rays of the low-hanging sun . `` Good-by , '' he said , smiling up at her from the steps . `` Do n't worry , please do n't .