Established by Edward L. Youmans APPLETONS' POPULAR SCIENCE MONTHLY EDITED BY WILLIAM JAY YOUMANS VOL. LIV NOVEMBER, 1898, TO APRIL, 1899 NEW YORK D. APPLETON AND COMPANY 1899 COPYRIGHT, 1899, BY D. APPLETON AND COMPANY. VOL. LIV. ESTABLISHED BY EDWARD L. YOUMANS. NO. 4. APPLETONS' POPULAR SCIENCE MONTHLY. FEBRUARY, 1899. _EDITED BY WILLIAM JAY YOUMANS._ CONTENTS. PAGE I. Vegetation a Remedy for the Summer Heat of Cities. By STEPHEN SMITH, M.D., LL.D 433 II. Mivart's Groundwork of Science. By Prof. WM. KEITH BROOKS 450 III. The Science of Observation. By CHARLES LIVY WHITTLE. (Illustrated.) 456 IV. Death Gulch, a Natural Bear-Trap. By T.A. JAGGAR, Jr. (Illustrated.) 475 V. The Labor Problem in the Tropics. By W. ALLEYNE IRELAND 481 VI. Principles of Taxation. XX. The Law of the Diffusion of Taxes. Part II. By the Late Hon. DAVID A. WELLS 490 VII. The Great Bombardment. By CHARLES F. HOLDER. (Illustrated.) 506 VIII. The Spirit of Conquest. By J. NOVICOW 518 IX. A Short History of Scientific Instruction. II. By Sir J.N. LOCKYER 529 X. The Series Method: a Comparison. By CHARLOTTE TAYLOR 537 XI. The Earliest Writing in France. By M. GABRIEL DE MORTILLET 542 XII. Sketch of Gabriel de Mortillet. (With Portrait.) 546 XIII. Correspondence: The Foundation of Sociology.--Evolution and Education again.--Emerson and Evolution 553 XIV. Editor's Table: The New Superstition.--Emerson 557 XV. Scientific Literature 559 XVI. Fragments of Science 569 NEW YORK: D. APPLETON AND COMPANY, 72 FIFTH AVENUE. SINGLE NUMBER, 50 CENTS. YEARLY SUBSCRIPTION, $5.00. COPYRIGHT, 1899, BY D. APPLETON AND COMPANY. Entered at the Post Office at New York, and admitted for transmission through the mails at second-class rates. [Illustration: GABRIEL DE MORTILLET.] APPLETONS' POPULAR SCIENCE MONTHLY. FEBRUARY, 1899. VEGETATION A REMEDY FOR THE SUMMER HEAT OF CITIES. A PLEA FOR THE CULTIVATION OF TREES, SHRUBS, PLANTS, VINES, AND GRASSES IN THE STREETS OF NEW YORK FOR THE IMPROVEMENT OF THE PUBLIC HEALTH, FOR THE COMFORT OF SUMMER RESIDENTS, AND FOR ORNAMENTATION.[1] BY STEPHEN SMITH, M.D., LL.D.