About nine o'clock on a dark April evening in the year 1866, a Berlin cab drove up the Wilhelmsstrasse with the trot peculiar to those vehicles, and stopped between the two lamps illuminating the door of No. 76, the house of the Minister for Foreign Affairs. The ground floor of this long two-storeyed house was well lighted up, and any one who peeped through the green blinds could see into many office-like rooms, well-filled with industrious writers, notwithstanding the lateness of the hour. The windows of the upper storey were only faintly lighted here and there.