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THE
POPULAR SCIENCE
MONTHLY
EDITED BY
J. McKEEN CATTELL
VOL. LXIX
JULY TO DECEMBER, 1906
NEW YORK
THE SCIENCE PRESS 1908
THE
POPULAR SCIENCE
MONTHLY
EDITED BY
J. McKEEN CATTELL
VOL. LXIX
JULY TO DECEMBER, 1906
NEW YORK
THE SCIENCE PRESS 1908