REPORT OF TUE .SECRETAIiY. 49 



The scieutilic work uyou ibe collection has been mostly doue iu con- 

 nection with the work of tbe Geological Survey. Professor Clarke is en- 

 gaged in an investigation of the chemical structnre of the silicates, and 

 tbere are also in i>rogress in his laboratory in the Mnseum building a 

 revision of the borates and a full series of analyses of the mineral tour- 

 maline. 



XVII. iJepartment of Lithology and Physical Geology. — The increase of 

 tbe department, though not so large as in the previous years, has been 

 healtby and symmetrical. Among the more important accessions may 

 be mentioned a collection of rocks and building stones of Mexico, ob- 

 tained by exchange from tbe Mexican Geographical Exploring Expedi- 

 tion; a series of tbe rocks of continental Euroi^e, obtained by exchange 

 from the museum at Annecy, Savoy; a series of typical marbles from 

 Pickens County, Georgia, gift of the Georgia Marble Company, and a 

 series of building stones obtained from the State commissioner of Soutb 

 Carolina at tbe Xew Orleans Exposition, and a vertical column repre- 

 senting the proportional thickness of the Archean, Cambrian, and Silu- 

 rian rocks of Xew Hampshire, obtained by exchange from Prof. C. H. 

 Hitchcock, 



Tbe exhibition series has continued to increase, and all the available 

 cases are already filled, and much material ready for disi)lay as soon as 

 others are constructed. Tbe time of tbe curator and his assistant has 

 been fully occupied in tbe development of the exhibition series, in the 

 preparation of copy for labels, and in the completion of classification of 

 tbe study series. A number of beautiful and instructive relief maps, 

 placed in tbe Museum by tbe U. S. Geological Survey, have been pro- 

 vided with cases and put on exhibition. Chief among these are the 

 models of Mount Taylor, Xew Mexico: Washoe District, Nevada; Eu- 

 reka District, Zsevada; Uinta and Wasatch Mountains, Utah,- Lead- 

 ville and vicinity, Colorado; the same in sections; High Plateaus of 

 Utah; Henry Mountains, Utah; stereogram of the Henry Mountains, 

 Utah; Elk Mountains, Colorado; Yosemite Talley, California, and the 

 Yellowstone National Park. Of the various exhibition series in process 

 of preparation, the collections of rock-forming minerals, the structural 

 series, litbological series, and the building and ornamental stones only 

 are iu condition approximating completion. Others, now under way, 

 though in a less advanced stage, are the three series classed under the 

 head of dynamical, structural, and historical geology. A portion of the 

 materials belonging to these series are already on exhibition, being of 

 themselves sufiicieutly striking in appearance to excite interest, though 

 not occui)ying their proper jilaces in the systematic collection. 



Tbe investigations of tbe curator, Mr. G. P. Merrill, have been directed 



chiefly toward tbe mineralogy of tbe District of Columbia, the origin and 



nature of fulgurites, the durability of building stones, besides studies on 



local petrograpy which are not yet ready for publication. Tbe curator 



H. Mis. 170 4 



