REPORT OF THE PRESIDENT, 1922. 7 



any other method of statement. It is worth noting that among the 

 books in press this year our interest ranges from the work by Barus, 

 on ''Displacement Interferometry applied to Acoustics and to Gravi- 

 tation," a fundamental work in mathematical physics, to studies like 

 those in Smith's monograph on "Gaseous Exchange and Physiological 

 Requirements for Level and Grade Walking," or, in another direction, 

 to the scholarly paper by Lowe and Rand on a recently discovered 

 fragment of Letters of Pliny the Younger, a study in palaeography. 



As evidence of the progress being made by the Institution, special 

 attention should be called to the issue in 1922 of the final parts of 

 the Pennsylvania volume in the " Index of Economic Material in the 

 Documents of the States of the United States, " by Adelaide R. Hasse. 

 This work concludes the series of publications in the Department of 

 Economics and Sociology initiated in 1907, and completes the studies 

 carried on over a period of 18 years. Volume III of the monographic 

 study of the cactus group by Britton and Rose, which has grown out 

 of the investigations of the Desert Laboratory at Tucson, is issued this 

 year just as the fourth and concluding volume is advanced to the 

 press. There is thus rounded out another important unit study 

 conducted under the auspices of the Institution. W. A. Cannon's 

 study of the floras of arid regions in Australia appeared at a time when 

 Dr. Cannon was engaged in a similar investigation of the floras of arid 

 areas in South Africa and India. John F. Hayford's volume on the 

 "Effects of Winds and of Barometric Pressures upon the Great Lakes" 

 represents the completion of data necessary to finish the first part of 

 this work. Under continued support from the Institution, Dr. Hayford 

 is now engaged in the second stage of these studies on an estimate of 

 the stream-flow and evaporation of the Great Lakes. Ralph W. G. 

 Wyckoff's paper, on "The Analj^ical Expression of the Results of the 

 Theory of Space-Groups," arising from studies in the Geophysical 

 Laboratory, is a contribution of importance appearing at a time when 

 this Laboratory, along with other agencies in the country, is attacking 

 questions relative to the atomic and molecular constitution of crystals 

 with a view to the ultimate bearing of such data on the problem of the 

 structure of matter. J. E. Weaver's work, on " Development and Activi- 

 ties of Roots of Crop Plants," is an unusual study of root variation bear- 

 ing upon fundamental biological problems and ultimately concerning 

 many questions in practical agriculture of the future. Walter W. Hyde's 

 volume on Victor Monuments is an investigation in the field of classics 

 presenting the results of long-continued study of monuments dedicated 

 to victory. It is one of the important additions to classical research 

 in the past year. 



