16 REPORT OF THE SECRETARY. 



The followiug are the rules which have been adopted for the distribu- 

 tion of the several publications of the Institution : 



1st. They are presented to learned societies of the first class which in 

 return give complete series of their publications to the Institution. 



2d. To libraries ol" the first class which give in exchange their cata- 

 logues and other publications, or an equivalent from their duplicate 

 volumes. 



3d. To colleges of the first class which furnish catalogues of their 

 libraf'ies and of their students, and all other publications relative to 

 their organization and history. 



4th. To States and Territories, provided they give in return copies of 

 all documents published under their authority. 



5th. To public libraries in this country, containing 15,000 volumes, 

 especially if no other copies are given in the same place ; and to smaller 

 libraries where a large district would be otherwise unsupplied. 



Gth. To institutions devoted exclusively to the promotion of particu- 

 lar branches of knowledge are given such Smithsonian publications as 

 relate to their respective objects. 



7th. The Annual Keports are presented to the meteorological observ- 

 ers, to contributors of valuable material to the library or collections, 

 and to persons engaged in special scientific research. 



The distiibution of the publications of the Institution is a matter 

 which requires much care and judicious selection, the great object being 

 to make known to the world the truths which may result from the ex- 

 penditure of the Smithson fund. For this purpose the principal class 

 of publications, namely, the Contributions, must be so distributed as to 

 be accessible to the greatest number of readers, and this will evidently 

 be to large central libraries. 



The volumes of Contributions are presented on the express condition 

 that, while they are carefully preserved, they shall be accessible at all 

 times to students and others who may desire to consult them, and be 

 returned to the Institution in case the establishments to which they are 

 presented at any time cease to exist. These works, it must be recol- 

 lected, are not of a popular character, but require profound study to 

 fully understand them; they are, however, of importance to the pro- 

 fessional teacher and the popular expounder of science. They contain 

 materials from which general treatises on special subjects may be elab- 

 orated. 



The publications of the Institution during the past j ear are mainly 

 those described in previous reports and which have been in process of 

 preparation for a series of years. They form two volumes of the Smith- 

 sonian Contributions to Knowledge, XX and XXI, made up of separate 

 papers. 



The twentieth volume of the Smithsonian Contributions to Knowl- 

 edge consists of one memoir only, entitled. The Winds of the Globe, or 



