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THE
POPULAR SCIENCE
MONTHLY
EDITED BY
J. McKEEN CATTELL
VOL. LXXIV
JANUARY TO JUNE, 1909
NEW YORK
THE SCIENCE PRESS
1909
THE
POPULAR SCIENCE
MONTHLY
EDITED BY
J. McKEEN CATTELL
VOL. LXXIV
JANUARY TO JUNE, 1909
NEW YORK
THE SCIENCE PRESS
1909