On September 16, 1896, after a period of very stormy wet weather, I saw a great migration of swallows down the Thames. It was a dark, dripping evening, and the thick osier bed on Chiswick Eyot was covered with wet leaf. Between five and six o'clock immense flights of swallows and martins suddenly appeared above the eyot, arriving, not in hundreds, but in thousands and tens of thousands. The air was thick with them, and their numbers increased from minute to minute. Part drifted above, in clouds, twisting round like soot in a smoke-wreath. Thousands kept sweeping just over the tops of the willows, skimming so thickly that the sky-line was almost blotted out for the height of from three to four feet.