698 THE AMERICAN NATURALIST. (VoL. XXXII. 
phenomena of nature thus illustrated embrace the action of 
mountain-building forces, of water, wind, and sand upon rock 
surfaces, and of volcanic activity of various kinds. The use of 
pictures is not only instructive, but is an addition to the 
attractiveness of the exhibit, and serves to call the attention of 
visitors to the specimens in the cases. The collection is well 
provided with descriptive and other labels. As proved by 
experience at Hildesheim, and also at the Natural History 
Museum in Paris, and at the Museum of Practical Geology, and 
the British Museum (Natural History) in London, such collec- 
tions illustrating general geology may be made not only instruc- 
tive, but attractive and somewhat popular as well. Here, even 
more than in some other departments of natural history, the 
popularity of the exhibit will depend largely upon the effective- 
ness of installation and arrangement and the clearness and 
completeness of labeling. 
The Rock Collection embraces more than 1000 specimens 
on exhibition, and, besides igneous and other crystalline rocks, 
includes samples of sandstones, limestones, and other sedi- 
mentary rocks. The specimens consist, for the most part, of 
well-trimmed blocks about six by four by one to one and a half 
inches in dimensions. They are arranged in trays, and each is 
accompanied by a neat, clearly written, comprehensive label. 
The classification is according to a scheme of which the tabu- 
lated elaboration lies at convenient points in the cases, and may 
also be obtained with the printed guide. That such a collection 
of rocks is highly valuable to the student for systematic study 
goes without saying; but it is also useful to the general public 
for reference, because the knowledge, and consequently the 
literature, of the subject of petrography is rapidly increasing at 
the present time, and the inquiry for such collections is also 
on the increase. Wooden-framed cases are used exclusively 
throughout the museum. 
Berlin.—The famous mineral collection of the Natural H istory 
Museum is arranged partly in wooden-framed cases with “A - 
shaped tops, the exhibition specimens being arranged on narrow 
steps in these tops, while the base is provided with drawers for 
` systematic storage. The cases display the minerals in an excel- 
