Number 15. A list of seismologic stations of the world. Compiled by Harry O. 

 Wood. July, 1921. Pages 142. Price $2.00. 



Volume 3 

 Number 16. Research laboratories in industrial establishments of the United States, 



including consulting research laboratories. Originally compiled by Alfred D. 



Flinn; revised and enlarged by Ruth Cobb. December, 1921. Pages 135. Price 



$2.00. 

 Number 17. Scientific papers presented before the American Geophysical Union at 



its second annual meeting. March, 1922. Pages 108. Price $1.50. 

 Number 18. Theories of magnetism. By members of the Committee on Theories of 



Magnetism of the National Research Council. A. P. Wills, S. J. Barnett, L. R. 



Ingersoll, J. Kunz, S. L. Quimby, B. M. Terry, S. R. Williams. August, 1922. 



Pages 261. Price $3.00. 



Volume 4 

 Number 19. Celestial mechanics. Report of the Committee on Celestial Mechanics 



of the National Research Council. E. W. Brown, G. D. Birkhoff, A. O. Leuschner, 



H. N. Russell. September, 1922. Pages 22. Price $0.40. 



Number 20. Secondary radiations produced by X-rays, and some of their applica- 

 tions to physical problems. Arthur H. Compton. October, 1922. Pages 56. 



Price $1.00. 

 Number 21. Highway research in the United States. Results of census by Advisory 



Board on Highway Research, Division of Engineering, National Research Council, 



in cooperation with the Bureau of Public Roads, United States Department of 



Agriculture. William Kendrick Hatt. October, 1922. Pages 102. Price $1.50. 

 Number 22. Mechanical aids for the classification of American investigators with 



illustrations in the field of psychology. Harold C. Bingham. November, 1922. 



Pages 50. Price $0.75. 

 Number 23. Certain problems in acoustics. Compiled by National Research Council 



Committee on Acoustics. November, 1922. Pages 31. Price $0.50. 

 Number 24. Electrodynamics of moving media. Report of the National Research 



Council Committee on Electrodynamics of Moving Media. W. F. G. Swann, 



John T. Tate, H. Bateman, E. H. Kennard. [In press.] 

 Number 25. Celestial mechanics. A survey of the status of the determination of 



the general perturbations of the minor planets. Appendix to the report of the 



Committee on Celestial Mechanics. A. O. Leuschner. [In press.] 



Volume 5 

 Number 26. Cooperation with the Federal Government in Scientific work. E W. Allen . 



December, 1922. Pages 27. Price $0.50. 



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