3S 
glaciers, such as Porfirio Diaz glacier, Mexico, and the Mer de 
Glace, Switzerland. 
CASE 2. — Types of structure. Jointed structure. Illus- 
trated. by basalt from Mt. Holyoke, Mass., Auvergne, France, 
and other localities. 
Jointed limestones and conglomerates. In one of the latter 
specimens the joint planes cut quite through the pebbles of the 
conglomerate, showing that the jointing has occurred subsequent 
to the formation of the conglomerate. Specimens illustrating 
cone-in-cone structure and stylolites. These are formed prob- 
ably by local pressure. 
Sand and limonite concretions from m.any localities. These 
have imitative shapes and hence are often taken for petrified 
objects of animal or vegetable origin. 
CASE 3. — Septaria. These are formed by the drying and 
shrinking of concretions and subsequent filling of the cracks 
with calcite. When cut and polished, as shown, they are ob- 
jects of great beauty. 
Large collection of geodes chiefly from the Keokuk, Iowa, 
beds. These are hollow, concretionary formations lined fre- 
quently with sparkling crystals of quartz. 
CASE 4. — Cave formations and cave life. Stalactites, stal- 
agmites and cave formations chiefly from Wyandotte and Mar- 
engo Caves, Indiana, mounted in natural position so as to illus- 
trate form and details of a typical limestone cave. Bats, blind 
fish, cray-fish and crickets are exhibited in the ‘‘cave,” showing 
living forms characteristic of such areas. 
CASE 5. — Large specimens of types already mentioned. 
Series of slabs illustrating glacial scoring and polishing of lime- 
stone obtained in the excavations for the Chicago Drainage 
Canal. Large concretions and septaria, and large ripple-marked 
slabs. 
Upon the wall are framed specimens of the so-called ruin 
marble, a rock in which the natural faulting and coloring have 
been such as to give to a slab an appearance like a painting of 
a ruined city. 
FLOOR OF HALL. — Case of specimens of clay concre- 
tions from various localities, showing varieties of form and 
size. 
