ADVERTISEMENT. 



The object of the General Appendix to the Annual Report of the 

 Smithsonian Institution is to furnish brief accounts of scientific dis- 

 covery in particular directions; reports of investigations made by 

 collaborators of the Institution ; and memoirs of a general character 

 or on special topics that are of interest or value to the numerous 

 correspondents of the Institution. 



It has been a prominent object of the Board of Regents of the 

 Smithsonian Institution, from a very early date, to enrich the an- 

 nual report required of them by law with memoirs illustrating the 

 more remarkable and important developments in physical and bio- 

 logical discovery, as well as showing the general character of the 

 operations of the Institution; and this purpose has, during the 

 greater part of its history, been carried out largely by the publica- 

 tion of such papers as would possess an interest to all attracted by 

 scientific progress. 



In 1880 the Secretary, induced in part by the discontinuance of 

 an annual summary of progress which for 30 years previous had 

 been issued by well-known private publishing firms, had prepared 

 by competent collaborators a series of abstracts, showing concisely 

 the prominent features of recent scientific progress in astronomy, 

 geology, meteorology, physics, chemistry, mineralogy, botany, zool- 

 ogy, and anthropology. This latter plan was continued, though not 

 altogether satisfactorily, down to and including the year 1888. 



In the report for 1889 a return was made to the earlier method of 

 presenting a miscellaneous selection of papers (some of them origi- 

 nal) embracing a considerable range of scientific investigation and 

 discussion. This method has been continued in the present report 



for 1920. 



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