REPORT OF ASSISTANT SECRETARY. 23 



Among the more important accessions have been several relief maps 

 received from the Geological Survey, a collection of rocks and building 

 stoues from Mexico, a series of the rocks of Continental Europe, and a 

 series of typical marbles and building stones from South Carolina, etc. 



There are several groups of exhibition specimens in process of prepara- 

 tion, among them being a structural series, a lithological series, and a 

 series of building and ornamental stones. These are in part on exhibi- 

 tion, though not in their proper places in the systematic collection. 



The curator, Mr. Merrill, is engaged in investigations upon the min- 

 eralogy of the District of Columbia, the origin and nature of fulgurites, 

 and the durability of building stones, besides carrying on studies on 

 local petrography; and has just completed a catalogue of the collection 

 of building stones now in the Museum. 



The total number of specimens in the collection is estimated at 

 20,647, of which 17,647 belong to the reserve series. Of the latter num- 

 ber 5,313 are on exhibition, 2,730 being specimens of building and orna- 

 mental stones, and 1,829 belonging to the educational series of rocks 

 and rock-forming minerals. There are, also, in the collection 3,400 

 thin sections of rocks prepared for microscopic study. -Of these nearly 

 200 have been added during the year. 



DEPARTMENT OF METALLURGY AND ECONOMIC GEOLOGY. 



Owing to the fact that so great a mass of material is already assigned 

 this department, which is under the curatorship of Mr. F. P. Dewey, it 

 has not been considered wise to solicit additional collections, although 

 much has been received during the year. 



The special attention of the curator has been given to the arrange- 

 ment and classification of the mass of material received from the Insti- 

 tute of Mining Engineers, part of which arrived during this year. 



The preparation of the exhibition series has been going steadily for- 

 ward, and a portion has been placed on exhibition as a preliminary dis- 

 play. The curator has commenced the preparation of a descriptive cata- 

 logue of the systematic collections, to serve as a guide to visitors. 



For three years past the curator has been employed in an investiga- 

 tion of the physical properties of coke, and has published a paper upon 

 the porosity and specific gravity of different kinds of this material. 



The total number of specimens in the collection is estimated at 48,000, 

 of which 17,000 are on exhibition. During the year 5,506 entries were 

 made, including 8,552 specimens. 



