INFORMATION TO CONTRIBUTORS 
The Proceedings is the official organ of the National Academy of 
Sciences and of the National Research Council for the publication of 
brief accounts of important current researches of members of the Academy 
and of the Council and of other American investigators, and for reports 
on the meetings and other activities of the Academy and of the Council. 
Publication in the Proceedings will supplement that in journals devoted 
to the special branches of science. The Proceedings will aim especially 
to secure prompt publication of original announcements of discoveries 
and wide circulation of the results of American research among investi- 
gators in other countries and in all branches of science. 
Articles should be brief. The viewpoint should be comprehensive 
in giving the relation of the paper to previous publications of the author 
or of others and in exhibiting, where practicable, the significance of the 
work for other branches of science. Elaborate technical details of the 
work and long tables of data should be avoided, but authors should be 
precise in making clear the new results and should give some record of 
the methods and data upon which they are based. 
Manuscripts should be prepared with a current number of the Pro- 
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References to literature, numbered consecutively, will be placed at the 
end of the article and short footnotes should be avoided. It is suggested 
that references to periodicals be furnished in some detail and in general 
in accordance with the standard adopted for the Subject Catalogue of the 
International Catalogue of Scientific Literature, viz., name of author, 
with initials following (ordinarily omitting title of paper), abbreviated 
name of Journal, with place of publication, series (if any), volume, year, 
inclusive pages. For example: Montgomery, T. H. f /. Morph., Boston, 
22, 1911 (731-815); or, Wheeler, W. M., Konigsburg, Schr. physik. Ges., 
55, 1914 (1-142). 
Papers by members of the Academy may be sent to Edwin Bidwell 
Wilson, Managing Editor, Mass. Institute of Technology, Cambridge, 
Mass. Papers by non-members of the Academy or Council should be 
submitted through some member. 
Proof will not ordinarily be sent; if an author ask for proof, it will be 
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to him. Authors are therefore requested to make final revisions on the 
typewritten manuscripts. The editors cannot undertake to do more than 
correct obvious minor errors. 
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SCHEDULE OF RATES FOR REPRINTS, CARRIAGE CHARGES EXTRA. 
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100 
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Copyright, 1921, by the National Academy of Sciences 
