REPORT OF THE SECRETARY. 



59 



institutes, and museums in the United States, and transmitted to sim- 

 ilar institutions in all parts of the world. 



Diagram showing increase of exchange transmissions, in tons of 2,000 pounds, from 1850 

 to 1912, divided into periods of Ave years each. 



For purposes of comparison, the number and weight of packages 

 of different classes are indicated in the following table : 



