Mabch 12, 1909] 



SCIENCE 



423 



drafting; while the student who nrnst, by 

 force of circumstances, be self-instructed, 

 could not be better provided therefor. 



The treatment of valve-motion is admirable. 

 The precedence given the Bilgram diagram 

 over the Zeimer, although unusual, is fully 

 warranted, the former being far superior for 

 designing, while possessing equal merits with 

 the latter for analysis. 



The frequent shaded perspectives will be 

 especially appreciated by the beginner in ma- 

 chine drawing, obviating, as they do, in con- 

 siderable degree, the necessity for the models 

 recommended but not always obtainable. 



Among the more important features ap- 

 pearing for the first time in this edition are 

 the " Course in Lettering " and the " Present 

 Practise in Drafting Room Methods," the 

 latter a summary of replies, from two hun- 

 dred of the leading engineering firms of this 

 country, to thirty-five questions as to shop 

 practise. An ample index completes this al- 

 together valuable work. 



Frederick N. Willson 



SCIENTIFIC JOURNALS AND ARTICLES 

 The February number (volume 16, number 

 5) of the Bulletin of the American Mathema- 

 tical Society contains the following papers: 

 " The Second Regular Meeting of the South- 

 western Section," by O. D. Kellogg; "Re- 

 marks Concerning the Second Variation for 

 Isoperimetric Problems," by Oskar Bolza; 

 " Notes on the Simplex Theory of Numbers," 

 by R. D. Carmichael; "The Solution of 

 Boundary Problems of Linear Differential 

 Equations of Odd Order," by W. D. A. West- 

 fall ; " A Class of Functions Having a Pecu- 

 liar Discontinuity," by W. D. A. Westfall; 

 " On Certain Determinants Connected with 

 a Problem in Celestial Mechanics," by 

 H. E. Buchanan ; " Sylvester's Mathematical 

 Papers," by L. E. Dickson; "Hilton's Finite 

 Groups," by Arthur Ranum ; " Shorter No- 

 tices": Ball-Freund's Histoire des' Mathema- 

 tiques, and Giinther's Geschichte der Mathe- 

 matik, by D. E. Smith; Tannery's Manu- 

 scrits de Evariste Galois and Minkowski's 

 Diophantische Approximationen, by L. E. 



Dickson; Sturm's Lehre von den geometri- 

 schen Verwandtschaften, Band IL, by Virgil 

 Snyder; Arnoux's Arithmetique graphique, 

 by W. H. Bussey; Enriques-Fleischer's 

 Fragen der Elementargeometrie, by H. E. 

 Hawkes; Poincare's Legons de Mecanique 

 celeste, by F. R. Moulton; Gutzmer Tatigkeit 

 der Unterrichtskommission, by J. W. A. 

 Young; "Notes"; "New Publications." 



The March number of the Bulletin con- 

 tains : " The Fifteenth Annual Meeting of 

 the American Mathematical Society," by F. 

 N. Cole; "The Winter Meeting of the Chi- 

 cago Section," by H. E. Slaught; "The 

 Sixteenth Meeting of the American Associa- 

 tion for the Advancement of Science," by G. 

 A. Miller; " Some Surfaces Having a Family 

 of Helic^ as One Set of Lines of Curvature," 

 by Eva M. Smith; "Note on Enriques's 

 Review of the Foundations of Geometry," 

 by A. R. Schweitzer; "Notes"; "New Publi- 

 cations." 



SPECIAL ARTICLES 



A POSSIBLE ERROR IN THE ESTIMATES OP THE BATE 



OF GEOLOGIC DENUDATION* 



The presentation at the Baltimore meeting 

 of the American Chemical Society of a paper 

 by Dole and Stabler on the rapidity of geo- 

 logic denudation recalls attention to a possible 

 source of error in such estimates which has 

 been already implied in the writings of 

 Walther, TJdden and other students of aeolian 

 geology. The peculiarly thorough and com- 

 prehensive figures of Dole and Stabler are de- 

 duced, as have been all previous ones, from the 

 examination of river waters, and are based 

 upon the assumption that all material which 

 is removed from the land to the sea is carried 

 in suspension or solution by outward-flowing 

 water. Recent studies on the magnitude of 

 asolian transport cast some doubt upon the 

 validity of this assumption. It has become 

 apparent that much surface material is moved 

 from place to place by seolian action and that 

 much of this transport is to be ascribed to the 

 slow and unnoticed^ but continuous, action of 



'Published by permission of the Secretary of 

 Agriculture. 



