6 REPORT OF THE SECRETARY. 



compass is situated. Tlence, in addition to swinging the Monadnock, or, 

 in other words, turning its bow in succession to every point of the horizon 

 to determine the deviations of her compasses from the true north, it was 

 necessary to make observations on terrestrial magnetism on shore, and 

 these, in their turn, required the determination of time, latitude, and 

 azimuth. The memoir is divided into five sections: 1st, introduction; 

 2d, description of stations; 3d, astronomical observations; 4th, observa- 

 tions on terrestrial magnetism ; 5th, observations on the magnetism of 

 the ship. The results obtained may be summed up as follows : The lati- 

 tude of seven points was determined. The magnetic declination, incli- 

 nation, and horizontal force were obtained at seventeen stations, eleven 

 of which were in South America. The ship was swung, and the devia- 

 tions of all her compasses, seven in number, were observed and compared 

 with those deduced from theory at ten places so situated as to afford 

 very great changes in the terrestrial magnetic elements. For all these 

 compasses the co-efficients or quantities necessary to reduce Poisson's 

 general equations were determined separately, with considerable accu- 

 racy. The agreement between theory and observation was found to 

 be sufficiently exact for the purposes of navigation, but not entirely 

 satisfactory in a scientific point of view. It appears from the results that 

 certain parts of the theory require further investigation; and from the 

 observations it is shown that when a vessel is swung for the first time 

 near where she was built it is impossible to make any reliable estimate 

 of the changes which the deviations of her compasses will undergo upon 

 a change of magnetic latitude. 



The memoir of Dr. E. W. Hilgard, on "The geology of Lower Louisiana, 

 including the Petite Ause region," mentioned in the last report, has been 

 received from the author, and the illustrations put in the hands of the 

 engraver. 



The work of Professor S. Newcornb, on "A new orbit of Uranus as 

 influenced by the perturbations of Neptune and other bodies," is srill in 

 progress. In the calculation of the tables for indicating the places 

 of Uranus, the assistance of Dr. Kampf, late of Germany, has been 

 secured at the expense of the Institution. The labors of Professor 

 Newcomb are gratuitously given for the advance of science. 



The articles for the Miscellaneous Collections mentioned in the last 

 report, viz: DeSaussure's "Monograph of hymenoptera," Uhler's "Mono- 

 graph of hemiptera," and Watson's "Botany of the region west of the 

 Mississippi," are still in the course of preparation, and some of them 

 will be published during the next year. 



The "Arrangement of the families of Mollusks," by Professor Theo- 

 dore Gill, described in the last report, has been published. It forms an 

 octavo pamphlet of 65 pages, and will be of importance in arranging 

 the specimens of the national museum, as well as those of other col- 

 lections in this country. 



A fourth edition of the " List of foreign institutions in correspon deuce 



