166 STUDIES FOR STUDENTS 
only consideration in the selection of stone to be used in the 
business portion of a large city should be strength and durability. 
In the suburban and resident parts of a city and in rural dis- 
tricts, where smoke and dust are trifling matters, the original 
color will not suffer seriously from external causes alone. In 
these places beauty is one of the chief ends of architecture, and 
a judicious scattering of light and dark colored stone buildings 
adds very materially not only to the appearance of the street as 
a whole, but also to the beauty of the dwellings individually. 
When used for interior decorations, a stone does not suffer 
materially from atmospheric agencies, and the color will ordi- 
narily remain permanent. The selection of stone for these uses, 
then, becomes largely a question of taste. A color which har- 
monizes with the surroundings or matches the other work, is 
generally considered most appropriate. In the flooring or steps, 
the capacity which the stone has to withstand abrasion without 
becoming unduly slippery, and not color, should be the control- 
ling factor. 
For monumental purposes the taste of the purchaser is again 
the main, controlling factor in the color selected. The stones 
used for monuments are mainly igneous and metamorphic 
(granite and marble), and as such contain few minerals which 
will result in discoloration. If pyrite or marcasite are constit- 
uents of the stone there will be danger of discoloration. How- 
ever, the fact that most of the water which falls upon a granite 
monument is shed by its polished surface, lessens the danger of 
discoloration, by preventing decomposition. 
In the more common uses to which stone is put, such as road 
making, sidewalks, retaining walls, cribs, breakwaters, bridge 
abutments, etc., the element of color seldom enters. In the 
case of retaining walls and sidewalks, which are partially orna- 
mental in nature, color should receive appropriate consideration. 
Il. INHERENT QUALITIES OF STONE 
The capacity which a stone has to withstand the forces tend- 
ing to destroy it, is known as durability, and depends upon the 
