7 p.m.
We were at twenty metres , still diving at the time . I consulted the chart , but could find no bottoming ground within fifty miles , a distance which was quite beyond my powers . At 11 p.m. I simply had to come up again and get a charge on the batteries . From 7 p.m. to 10 p.m. , at regular half-hourly intervals , a depth-charge had gone off somewhere within a radius of two miles of me . Needless to say , I was only crawling along at about one knot and altering course frequently . What was so terrible was the patent fact that the patrols in this area had evidently got some device which enabled them to keep in continual touch with me to a certain extent . These monotonous and regular depth-charges seemed to say : `` We know , Oh !