~V~A4p/~vN

January 21a 194?
Dr. David Thompson
Cook County Forest Preserve
536 N. Harlem Ave.
liver Forest, Illinois
Dear Dave:
I hope you will do some further thinking on the
subjeot matter of your letter to P=uIl 'rrington
of Deceber 16.
David Look. the British ornithologist, has been
here this week and he contributed a further thought
which tends to support yours. He saye that
athambtically speaking, a simple cycle with a
true periodicity V   have a  imle cause rather
than a complication of variable causes.
With personal regards, yours as ever,
Aldo 1eopold

00 arrinston