51 
effects are produced where air has had long access to the ma- 
terial in the ground and has caused oxidation of the iron con- 
tained in the specimens. 
CASE 7— Marbles, United States. The most widely used 
United States marbles, all of which are .illustrated here, are the 
Vermont, Georgia and Tennessee marbles. The Vermont mar- 
bles are fine textured and range in color from pure white through 
gray to black. The coarsely crystalline, brilliant marbles from 
Georgia run from white into the pinks. It must not be thought 
trom the appearance of the case that colored marbles, such as 
appear m the collection from foreign localities, do not exist in 
the United States. Deposits are known but for various reasons 
remain unworked. 
CASES 8 AND 9.— Marbles and gypsums. Great Britain 
and Japan. The best known of these is the encrinal marble of 
Devon, England. 
The spheres are manufactured in Japan and exported as 
curiosities. 
CASE 10. — Granites and eruptive rocks. 
Owing to their hardness and the consequent expense of 
working, these stones are not so frequently polished as the 
marbles, but, as illustrated by these specimens, when polished 
they often present very beautiful effects. 
CASES 11 TO 15 contain a systematic collection of build- 
ing stones in the form of four-inch dressed cubes. 
CASE 11.— Limestones and marbles. Four-inch cubes of 
many of the limestones and marbles of the United States used 
for building. 
CASE 12. Sandstones. Four-inch cubes of many of the 
sandstones of the United States used for building purposes. 
CASE 13. Granites. Four-inch cubes of many of the gran- 
ites of the United States used for building purposes. The above 
four kinds of rock constitute nearly all the valuable building 
stones used in temperate climates. 
CASE 14.— Building stones of Mexico and Ecuador. These 
are mostly volcanic rocks, lavas and tuffs, which are sufficiently 
durable for mild climates and yet soft enough to be easily 
worked with simple tools. The building stones from Ecuador 
are ordinary pumice-stone. 
