342 SIMGIDMES JAM: SIMOIQIEIN IES, 
Estimates of the strength and durability of a stone from 
physical tests are usually based upon the following determina- 
tions: 
1. Strength, 
a. Compressive, 
6. Transverse. 
2. Elasticity, modulus of. 
Flardness — coefficient of wear. 
Specific gravity. 
Porosity. 
Weight per cubic foot. 
Effect of Temperature changes, 
a. Freezing and thawing of included water, 
b. Effect of extreme heat. 
8. Effect of gases, 
a. Carbonic acid, 
N Ow Hw 
6. Sulphurous acid. 
Attempts have been made to classify these tests under 
“strength tests” and ‘durability tests,’ but the classifications 
thus made are not logical because some of the tests have a 
double significance. 
STRENGTH 
A knowledge of the strength of a stone implies a familiarity 
with its capacity to withstand both compressive and tensile 
stresses. For this reason both the crushing strength and mod- 
ulus of rupture should be determined. 
Crushing strength — Up to within a few years the compressive 
strength test, by means of which the crushing or ultimate 
strength is determined, has been used for estimating both the 
durability and strength of a stone. However, a stone with a 
low crushing strength may be more durable than one in which 
the crushing strength is high. For this reason the crushing 
strength, alone, is insufficient for estimating the durability of a 
stone. In the absence of other tests the importance of the 
crushing strength has been frequently overestimated. 
