REPORT OF THE SECRETARY. 25 



ceedings of the National Museum, special reports on particular sub- 

 jects of biological or jihysical research, tabular compilations of classifi- 

 cation, naturul constants, and such other miscellaneous information as 

 is deemed of value to the scientific worker or student. Tliis series num- 

 bers twenty-one volumes, averaging about 800 pages each. The third 

 series comprises the Annual Eeports of the Eegents, presented to and 

 published by Congress. Accompanying the report proper (giving the 

 statistical and financial summaries required by law) interesting records 

 of particular advances and discoveries, or of the progress of science 

 generally, have been presented in a general appendix, making the 

 volume much sought after. 



Smithsonian Contributions to Knowledge. — Of the quarto class of pub- 

 lications the following memoirs have been collected and published during 

 the past year, as volume XXIII of the "Contributions to Knowledge," 

 forming a volume of 767 pages, illustrated by 155 wood-cuts and IG 

 plates : 



1. Introduction, contents, &c., IG images. 



2. Lucernarise and their allies; a memoir on the anatomy and i)hysi- 

 ology of Haliclystus Auricula and other Lucernarians, with a discus- 

 sion of their relations to other Acaleph», to Beroids, and Polypi. P>y 

 Henry James Clark, B. S., A. B. (Published April, 1878.) 4to, 1,38 pp., 

 4 wood-cuts and 11 plates, containing 145 figures. As stated in the 

 report for 1878, the lamented author died while his work was passing 

 through the press. 



3. On the geology of Lower Louisiana and the salt deposit on Petite 

 Anse Island. By Eugene W. Hilgard, Ph. D., professor of chemistry 

 in the University of Mississippi. (Published June, 1872.) 4to, 38 pp., 

 C wood-cuts. 



4. On the internal structure of the earth, considered as aftecting the 

 phenomena of precession and nutation ; supplementary to an article 

 under the above head in Smithsonian Contributions to Knowledge, vol. 

 XIX., No. 240, being the third of the problems of rotary motion. By 

 J. G. Barnard, U. S. Army. (Published August, 1877.) 4to, 20 pp., 

 4 wood-cuts. This memoir is a continuation of the mathematical dis- 

 cussion of an important problem of gyratory motion, published in 1872, 

 resulting in a modification of the conclusion formerly arrived at by t^he 

 author, and at the same time controverting the celebrated memoir of 

 Mr. Hopkins, which had been supposed to demonstrate that the terres- 

 trial gyration known as the "precession of the equinoxes" is incom- 

 patible with a molten or lluid interior to our globe. The question of 

 the internal fluidity of our earth thus appears to be now left (as for- 

 merly) to be settled by purely geological evidences. 



5. A Classification and Synopsis of the Trochilidce. By Daniel Gi- 

 raud Elliott, E. E. S. E. (Published March, 1879.) 4to, 289 pi>., 127 

 wood-cuts. This work comprises a full descrii)tion of every known spo- 



