74 
CASE 10. — Asbestos. These specimens are of asbestos as 
mined and are not confined to the commercially valuable material 
but include also many specimens of grades which at pr'eseht are 
of little economic importance. Consequently all stages between 
a merely compact but somewhat columnar tremolite and the 
finely fibrous flexible asbestos of the best quality may be traced 
through these specimens. 
CASE 11. — Mica. Besides the thin plates of mica of the best 
quality from leading American and Russian quarries, 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 the mica occurs are also shown. 
CASES 12 AND 13. — ^Abrasives. Corundum, emery, garnet,, 
sand and pumice stone are the more important minerals of this 
case. Other useful abrasives are represented by obsidian and 
feldspar. The rocks and minerals associated with emery are 
characteristic and should be examined in connection with the 
emery itself. The great variety in mineralogical composition 
of the abrasives should be noted. Carborundum and crushed 
steel represent the class of artificial abrasives. 
PLATFORM NO. 16. — Large specimens of gypsum and 
fluor spar. Large specimens of rock salt and epsomite or natu- 
ral epsom salts. Large specimens of natural sulphate of sodai 
(Glauber's salt). Salt from Stassfurt, Prussia. 
CASE 15. — Applications of asbestos. 
CASE 17. — The Leblanc process for the manufacture of 
soda. All stages of the process are illustrated by specimens of 
the raw, intermediate and final products. The relations of the 
various products to each other are indicated by the connecting 
lines. 
CASE 38. — The ammonia process for the manufacture of 
soda. This process is fully illustrated by a series of the raw ma- 
terials, intermediate and final products being so arranged that 
the process may be followed step by step. The electrolytic pro- 
cess for the manufacture of soda is illustrated in the same man- 
ner. 
