52 
of laminae or thin plates, which may be afterwards cut to unifom 
sizes and used for roofing. 
HALL 69. 
COALS OF THE UNITED STATES. 
Here one may study the distribution and extent of the coal 
fields of the United States, also the kinds of coal produced by 
each and the available means of transportation. 
On a large plate-glass map in the center of the hall, scale ten 
miles to one inch, the coal fields of the United States as at present 
developed are indicated by areas in black, and the 'principal rail- 
roads connecting them are also represented. 
Cases 1-18.— Specimens taken from these different fields, 
the exact locality of each being shown by figures on the 
labels corresponding to those on the map. The order of numbers 
is the same as the alphabetical order of the States. The speci- 
men labels show the uses of the coal, the names of the operators 
of the mines, the means of transportation, the markets, and the 
analyses of the specimens. Other data will be given to any one 
desiring to obtain them, on application to the Curator. 
HALL 70. 
COALS AND HYDROCARBONS. 
This hall contains a series of the carbon minerals, beginning 
with the diamond, and passing through graphite, the coals (an- 
thracite, semi-anthracite, semi-bituminous, bituminous and lignite) 
to bitumen and asphalt. 
Case lA — Diamonds from Kimberly Mines, South Africa. 
“Blue ground” or matrix in which diamonds occur, from De 
Beers mines, Cape Colony, South Africa. 
Case IB.— Graphite. Coke and the bye-products of the coke 
ovens. From these bye-products are obtained ammonia, most 
