Rocks and Soil 293 



Rocks Used for Buildings. Among the materials which the 

 rocks of the earth furnish for the use of man are stones for the 

 erection of large public buildings, residences, monuments, dams 

 and other engineering structures. The kinds of stone most popular 

 for building purposes are granite, marble, sandstone and limestone. 



Qualities of Building Stone. According to Dr. George P. 

 Merrill, expert on stone quarry statistics, the essential qualities 

 of stone for ordinary building are durability, permanence of 

 color, crushing strength and elasticity, and cheapness. 



It is claimed that : "A good building stone, whatever its kind, 

 should possess a moderately fine and even texture, with grain 

 well compacted; should give out a clear, ringing sound when 

 struck with a hammer, and show always a clear, fresh fracture. 

 It should also be capable of absorbing only a proportionately 

 small amount of water." It is difficult, if not impossible, to find 

 a type of building stone that meets all of these conditions. A 

 type that is durable and strong may lack permanency of color, 

 or a type that is durable and has permanency of color may lack 

 strength and elasticity. Then, in every type, the expense of 

 quarrying it and transporting it may be prohibitive, even when all 

 other qualities apparently are present. 



Granite. In all ages, granite has been regarded as one of the 

 most durable, strongest and most desirable of building stones. It 

 is extensively used for walls, 

 massive masonry of dams, pol- 

 ished columns of buildings, and 

 monuments. The best granites 

 in the United States are found 

 in the New England states, and 

 in Virginia, Missouri, and Min- 

 nesota. 



Sandstone. Sandstones, as 

 the name indicates, are made 

 up of sand grains. These are GRANITE ROCK 



firmly cemented together by Hard d ra We building stone, 



silica, carbonate of lime, iron oxide, or some clayey material. 

 Their durability depends more upon the character of these bind- 



