26 REPORT OF THE SECRETARY. 



CORRESPONDENCE. 



The correspondence of the Institution during the past year, especially 

 on account of the Centennial Exhibition, was very largely increased, 

 and has formed no inconsiderable part of the labors of the officers. The 

 usual number of inquiries have been made as to the name and character 

 of specimens of natural history, mineralogy, &c. The number of scien- 

 tific problems received for solution has not been diminished. Several 

 elaborate treatises have been submitted to the Institution for examina- 

 tion, purporting to be explanations of the theory of gravitatiou, and 

 other extended generalizations of natural phenomena. As the theory 

 of gravitation is a prominent subject of investigation by those who arc 

 interested in scientific speculations, we would direct attention to a paper, 

 published in the appendix to this report, prepared for the Institution by 

 Mr. William B. Taylor, of Washington, giving a history, with comments, 

 of all the attempts which have been made since the discoveries of New- 

 ton to the present time to refer the phenomena of gravitation to some 

 other cause than that of action at a distance. This elaborate paper will 

 exhibit the difficulties of the problem which those who endeavor to solve 

 it have to contend with, as well as the entire failure of all the attempts 

 which have been made and the probable result of all that will be here- 

 after essayed in regard to it. 



Among the subjects to which attention has been called by foreign cor- 

 respondents is that of the organization of a society, under the auspices 

 of the King of Belgium, at Brussels, for a thorough exploration of the 

 African continent, the final object of which being the suppression of 

 the slave-trade, the opening of the country to foreign commerce, and 

 its advancement in civilization. To this enterprise the attention of all 

 the geographical societies of the world is called, and their co-operation 

 solicited. It is proposed to run lines of survey across the continent 

 from east to west and from north to south, establishing depots at inter- 

 vals for the accumulation of articles of commerce and the supply of the 

 explorers. This is truly an enterprise worthy of the present age, since 

 its object is to open, for the uses of civilized man, a portion of the earth 

 richly endowed with the means of the support and the enjoyment of 

 human life, now almost a waste, or only sparsely inhabited by barbarian 

 tribes. It is a work to which the attention of our educated citizens of 

 pure African descent should be directed, as opening a field of unpar- 

 alleled usefulness in the way of advancing the civilization of the world, 

 and it is one to which they are especially adapted, since, in a letter from 

 Professor Edw. D. Blyden, of Liberia College, published in the appen- 

 dix to the Smithsonian Beport for 1870, it is shown that only individu- 

 als of pure African blood are fully fitted for withstanding the peculiar 

 inflneuce of the climate. 



EXCHANGES. 



The operations of this part of the geueral system of labor of the Insti- 

 tution have assumed a magnitude during the past year far greater than 



