50 REPORT OF NATIONAL MUSEUM, 1900. 



From the series of jointed sandstones from the Black Hills collected 

 by Mr. N. H. Darton, of the United States Geological Survey, and 

 mentioned in mj' last annual report, have been selected for exhibition 

 the typical series shown in Plate 5. The sharpness and clear-cut nature 

 of the faulting, together with the comparatively small amount of dis- 

 plac(Uiient, render such blocks almost ideal for the purpose of exhibi- 

 tion. Advantage has been taken of opportunities for procuring exam- 

 ples of the peculiar concretionary forms of granitic rocks known to 

 the Germans as ' * kugel '^ granites and otherwise as orbicular or con - 

 cretionary granites. Such have been studied and described by Krut- 

 schoff, who regards them as contact phenomena and as due to the 

 cr3'stallizing of the granitic material about preexisting fragments of 

 other rocks. One of the more striking forms from Sweden is shown 

 in Plate 6. 



The meteorite collection, to which reference has already lieen made, 

 comprises 742 specimens, representing 349 falls. This places it among 

 the large collections of the world, being only excelled, so far as we 

 have knowledge, by those of Paris, London, Vienna, and the ])ri^■ate 

 collections of Prof. H. A. Ward and Mr. C. S. Bement. 



The collections in the Division of Mineralogy are practically all 

 labeled, and a case at the south end of the hall has been prepared for 

 the reception of the Shepard collection of minerals already noted. 

 The text for a catalogue of the gem collection is well under way. 



The question of getting a maximum number of specimens into a case 

 with a minimum amount of interference or shadow has been quite 

 satisfactorily solved, so far as the Section of Vertebrate Paleontology 

 is concerned, b}^ the means shown in Plate 7. As will be noted, shelv- 

 ing is quite done awa}' with, with the exception of that afforded by the 

 bottom of the case and two narrow shelves at the top for large and 

 heavy materials which are often ''out of classification"' as compared 

 with the rest of the exhibit. The fossils are cemented to encaustic 

 tiles which arc of standard sizes, in units of 4-inch width, and which 

 are prevented from falling forward through some sudden jar ))y an 

 overlapping edge of wood at the top. By actual trial it has been 

 found that, though an apparently wasteful method of installation, so 

 far as space is concerned, more material can be actually put into a case 

 than when the ordinary horizontal or sloping shelf is used, and, more- 

 over, the view of one specimen is never obscured b}' one in front or 

 shadowed from alcove. The possibly objectionable features thus far 

 discovered are that it limits the size and weight of the specimen 

 exhibited and n(H'essitates the cementing of the samples to the tiles. 

 The first-mentioned o])jection has proved thus far mainly theoretical, 

 space for the larger specimens being readily found on the bottom or 

 on the narrow shelves, while the second is avoided l)y not including in 

 the series materials that would be injured or whose value would be in 

 any way impaired by the cementing process. 



