OF THE

STATE OF PENNSYLVANIA

FOR THE

PROMOTION OF THE MECHANIC ARTS FOUNDED 1824

Year Book---1923

PHILADELPHIA

HALL OF THE INSTITUTE

15 SOUTH SEVENTH STREET

SEPTEMBER 1, 1923

BY

W. J. HUMPHREYS, C.E., PH.D.

PROFESSOR OF METEOROLOGICAL PHYSICS, UNITED STATES WEATHER BUREAU, WASHINGTON, D. C.

665 PAGES, NUMEROUS ILLUSTRATIONS AND DIAGRAMS, INDEX, OCTAVO'. BOUND IN CLOTH

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THE FRANKLIN INSTITUTE

PHILADELPHIA

THE physical phenomena of the earth's atmosphere are exceedingly numerous and of great importance. Nevertheless, the explanations, even of those well understood, still remain scattered through many books and numerous journals. Perhaps this is because some of the phenomena have never been explained, and others but imperfectly so, but, however that may be, it is obvious that an orderly assemblage of all those facts and theories that together might be called the Physics of the Air would be exceedingly helpful to the student of atmospherics. An attempt to serve this useful purpose, begun in a course of lectures at the San Diego Aviation School (Rockwell Field) in 1914, led to the production of the following chapters-revised and reprinted from the Journal of The Franklin Institute, 1917, 1918, 1919, 1920.

The author begs to express his indebtedness to Prof. C. F. Marvin, Chief of the United States Weather Bureau, for numerous helpful criticisms; to Dr. C. F. Brooks, Editor of the Monthly Weather Review, for many excellent suggestions; to Prof. C. F. Talman, Librarian of the United States Weather Bureau, for valuable aid in locating original sources; and to Major R. B. Owens, D. S. O., Secretary of The Franklin Institute, for his encouraging interest in the work and invaluable attention to the details of its publication.

CONTENTS

INTRODUCTION

PART I

Mechanics and Thermodynamics of the Atmosphere, 16 Chapters.

PART II

Atmospheric Electricity and Auroras, 2 Chapters.

PART III

Atmospheric Optics, 8 Chapters.

PART IV

Factors of Climatic Control, 5 Chapters, and Appendices.

"It constitutes a notable addition to the literature of meteorology * * * * There has, up to the present, been no trustworthy English text-book which discussed the subject from so scientific a viewpoint or dealt with its modern developments so completely." Nature, London, May 23, 1918, page 231.

"The most thorough American work on general meteorology **** The purpose of the work is to present a comprehensive, explanatory statement of the physics of the air; one which may form the basis for new courses in meteorology in College and University Departments of Physics **** The scope of the book is all that is implied in the title, the physics of the air."

Monthly Weather Review, Washington, D. C., December, 1918, page 562.

"No first-rate comprehensive book on meteorology written from the standpoint of the physicist exists, at present, in any language, and there is perhaps no more striking gap in the literature of science. Dr. Humphreys's book will go a long way toward filling this gap. It is especially remarkable for the amount of skill and labor the author has devoted to checking, verifying and in many cases discrediting doctrines and ideas that have heretofore been passed on from one meteorological writer to another without critical examination." Scientific American, New York, June 19, 1920, page 669.

"Students of the science of the atmosphere have read with interest and appreciation the articles by Professor W. J. Humphreys of the Weather Bureau of the United States, on various aspects of the physics of the atmosphere which appeared from time to time in the Journal of The Franklin Institute of Philadelphia during the years 1917-20. The reproduction of these articles, revised and collected into a book for publication by the Institute, is a notable and welcome event in the history of the study of the air. **** The book is fully illustrated with many excellent diagrams and photographs excellently reproduced. **** Apart from the general excellence of the book and the presentation of its material, the parts which impress one most on reading them for the first time are the chapters on thunderstorms and lightning, atmospheric electricity and auroras, and atmospheric optics, as examples of close physical reasoning, and the chapters on factors of climatic control as an example of reasoning of a more general character. * * * * He deserves our hearty thanks for a very useful and handy book of reference indispensable for the meteorological library."

Sir Napier Shaw in Nature, London, March 17, 1921.