*The Correlation between the migratory flights of birds and certain accompanying meteorological conditions, by Frank Smith, pp. 32–35, State of Illinois, Circular No. 151, 1921, pp. 21–29, (weather maps April 29, 1909, May 7, 1916); 2 days of remarkable migrations are shown on p. 28. On both days the barometric gradients for S. winds were very strong.