8i> FIELD MUSEUM OF NATURAL HISTORY 
are next represented by full-sized models. In the floor cases 
of the hall several hundred specimens of cut gems and ornamental 
stones are shown. These include topazes, amethysts, emeralds, 
tourmalines, moonstones, rock crystal, amber, etc. The speci- 
men of carved amber is especially remarkable as a piece of lap- 
idist’s work. The series also includes a number of jasper vases 
and trays from the Urals and pieces of polished serpentine and 
onyx. A complete series of models of the famous diamonds 
of the world, illustrating their size, form, and color, makes a 
part of the exhibit. The Chalmers crystal collection, which 
includes about 250 specimens from United States localities and 
is the most complete collection of the kind ever made, occupies 
one case. 
Hall 65. 
STRUCTURAL AND DYNAMICAL 
GEOLOGY. 
The specimens in this hall for the most part represent phe- 
nomena met with in the study of the earth’s crust, and illustrate 
phases of rock structure and formation. Entering from 
Hall 64, in the first case at the left are shown large slabs 
with ripple-marked surfaces. One of the largest of these shows 
also cross ripples. Large surfaces exhibiting fossil mud cracks 
are also shown. In the next case the different results of glacial 
action are chiefly illustrated. The series includes glaciated peb- 
bles and boulders from glacial regions of Switzerland and Mex- 
ico, also from Chicago and Rochester, New York. Among the 
most interesting of the specimens are a series of boulders of cop- 
per found for the most part about the southern end of Lake 
Michigan which were brought by glacial movement from the cop- 
per-bearing regions about Lake Superior. The largest of these 
boulders weighs 375 pounds. Rock surfaces, planed and striated 
by glacial movement, are also shown. These are from both an- 
cient and modern glaciers. Specimens illustrating the effect of 
erosion by wind and water, also stages and forms of rock 
weathering are shown in this case. The next two cases are 
largely devoted to concretions and the collection there exhibited is 
perhaps the most complete one of these varied forms to be seen in 
any museum. Various forms of lime concretions, barite concre- 
