INFORMATION TO CONTRIBUTORS 
The Proceedings is the official organ of the Academy for the publica- 
tion of brief accounts of important current researches of members of the 
Academy and of other American investigators, and for reports on the meet- 
ings and other activities of the Academy. Publication in the Proceedings 
wiU 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 investigators in other countries and in all branches of science. 
Articles should be brief, not to exceed 2500 words or 6 printed pages, 
although under certain conditions longer articles may be published. 
Technical details of the work and long tables of data should be reserved for 
publication in special journals. 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. The viewpoint should be comprehensive in giv- 
ing 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. 
Manuscripts should be prepared with a current number of the Proceed- 
ings as a model in matters of form, and should be typewritten in duplicate 
with double spacing, the author retaining one copy. Illustrations should be 
confined to text-figures of simple character, though more elaborate illustra- 
tions may be allowed in special instances to authors wiUing to pay for their 
preparation and insertion. Particular attention should be given to arranging 
tabular matter in a simple and concise manner. 
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 accord- 
ance 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*, /. Morpk, 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 Bid well Wilson, 
Managing Editor, Mass. Institute of Technology, Cambridge, Mass. Papers 
by non-members should be submitted through some member. 
Proof will not ordinarily be sent; if an author asks for proof, it will be 
sent with the understanding that charges for his corrections shall be billed 
to him. Authors are therefore requested to make final revisions on the type- 
written manuscripts. The editors cannot undertake to do more than correct 
obvious minor errors. 
Reprints should be ordered at the time of submission of manuscript. 
They will be furnished to authors at cost, approximately as follows: 
Reprints of 2 pp. 4 pp. 6 pp. 8 pp. Covers extra 
Charge for first 100 copies $1.40 $2.00 $3.25 $3.25 $2.75 
Chargefor additional 100s V .45 .75 1.40 1.40 1.00 
(The charge for fewer than 100 copies is practically the same as for 100.) 
Copyright, 1919, by the National Academy of Sciences 
