REPORT OF THE SECRETARY. 9 
Chemical Influence of Light,” by Mr. Alfred Tuckerman, belongs to the 
growing class of reference aids to investigators and students, rendered 
necessary by the rapidly increasing volume of scientific literature. 
In the Miscellaneous Collections for the year a number of articles 
from the general appendix to the annual reports, commonly prepared 
at the expense of the Institution, have been considered worthy of re- 
publication as separate essays, and will probably find their place ulti- 
mately in volumes of this series. 
Smithsonian annual reports—The annual report of the Regents to 
Congress on the operations and condition of the Institution for the year 
ending June 30, 1888, was received more promptly than usual, and has 
been largely distributed. The annual report of the Regents on the 
operations and condition of the U. S. National Museum for the same 
period has also been received and widely distributed. The annual 
report of the Regents to Congress on tle Institution, for the year end- 
ing June 30, 1889, has in addition been received and distributed, and 
the annual report of the Secretary to the Board of Regents for the 
year ending June 30, 1890, has been issued during the year. 
A full descriptive list of the Smithsonian publications for the year 
will be given in the appendix. 
SMITHSONIAN INTERNATIONAL EXCHANGE SERVICE. 
The work of the Smithsonian Institution through which it is perhaps 
most widely known is its exchange service, whereby in a direct and 
tangible manner it effects one of the objects of its founder, ‘“ the diffu- 
sion of knowledge among men.” 
The exchange service was established very early in the history of the 
Institution, when communication between scientific men, particularly 
between those of the Old and of the New World, was slow and expen- 
sive. Its object was to distribute the Smithsonian publications, and to 
furnish at the same time a channel through which the publications of 
scientific men, societies, and institutions in this country might be sent 
to correspondents abroad, and similar publications from abroad might 
bereceived and distributedin America. The Institution received hearty 
codperation in every direction. The chief learned societies in different 
parts of the world offered their aid as distributing centers of exchange 
documents, and many of the larger steamship companies generously 
consented to carry exchange boxes free of freight charges; foreign gov- 
ernments gave their aid, and in 1854 Prof. Henry announced in his 
report that there was “no port to which the Smithsonian parcels are 
shipped where duties are charged on them, a certified invoice of con- 
tents by the Secretary being sufficient to pass them through the custom- 
house free of duty. On the other hand, all packages addressed to the 
Institution arriving at the ports of the United States are admitted 
Without detention, duty free. This system of exchanges is therefore 
