72 
Case 12. — Abrasives. The rocks and minerals associated 
with emery are characteristic and should be examined in connec- 
tion 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. 13. — Large specimens of gypsum andfiuor spar. 
Large specimens of rocksalt and epsomite or natural epsom salts. 
Large specimen of natural sulphate of soda {Glatibe?'s salt). 
Salt, Stassfurt Prussia. 
Case 15. — Applications of Asbestos., 
Case 16, — 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 relation of the various pro- 
ducts to each other are indicated by the connecting lines. 
Case 17. — The ammonia process for the manufacture of soda. 
This process is fully illustrated by a series of the raw materials, 
intermediate and final products so arranged that the process may 
be followed step by step. 
HALLS 73. 74 AND 75. 
Hall 73. — Ofl&ce of the Department of Geology. 
Hall 74. — Library of the Department of Geology. The works 
in this library treat of geology and kindred subjects, and are in- 
tended primarily for the use of officers of the Department. On 
application to the Curator, however, opportunity will be given to 
visitors to consult any special work. 
Hall 75. — Laboratory of the Department of Geology. 
