DEPARTMENT OF GEOLOGY 
65 
Nitrates are represented by several varieties of the soda nitre 
of Chili and by cave earths from caves in various parts of the 
world. 
Mica is represented by a series of specimens mainly from 
American and Russian quarries. Besides thin plates of mica 
of the best quality, specimens of low grade material enable the 
visitor to note the difference between the ordinary micas and the 
more valuable kinds. The rocks in which mica occurs are also 
shown. 
Asbestos is represented by two series, one of crude mineral 
and one illustrating its uses. These specimens are of asbestos 
as mined and are not confined to the commercially valuable 
material. Consequently all stages between a merely compact 
but somewhat columnar tremolite and the finely fibrous, flexi- 
ble asbestos of the best quality may be traced through these 
specimens. 
Phosphates are represented by a large series of specimens 
classified as mineral phosphates, rock phosphates, and guanos. 
The principal localities represented are Tennessee, Carolina, 
Florida, Russia, Spain, Venezuela, and Cuba. 
Gypsum is represented by a separate collection of specimens 
from many parts of the world, including the coarser kinds 
mined for land plaster, plaster-of-Paris, wall plaster, etc., and 
the finer varieties, selenite, alabaster, and satin spar, quarried 
for ornamental purposes. 
Native sulphur and those metallic sulphides from which 
sulphur is regularly extracted form a single collection. With 
these specimens is a series illustrating the various forms in 
which sulphur reaches the market. 
Processes for the manufacture of soda are illustrated by 
three collections. One shows the Leblanc process, all stages of 
which are illustrated by specimens of the raw, intermediate, and 
final products. The relations of the various products to each 
other are indicated by connecting lines. 
The ammonia process is fully illustrated by a series of the 
raw materials, intermediate and final products being so ar- 
ranged that the process may be followed step by step. The 
electrolytic process is illustrated in the same manner. 
