THE PROPERTIES OF BUILDING STONES, ETC. 343 
At the present time, however, it is argued by some that it is 
folly to determine the crushing strength, except in cases where 
the strength of the stone is very doubtful. Nevertheless, I do 
not believe that it is wise to encourage the abandonment of the 
crushing strength test. 
Architects using stone with which they are not familiar, are 
glad to avail themselves of all crushing strength data. In fact, 
the only intelligible method of expressing the strength of a 
stone to one not thoroughly familiar with the interpretation of 
the mineralogical composition and texture, is in pounds per 
square inch. 
Other than this the crushing strength determinations have an 
important scientific bearing upon problems in dynamic geology, 
and for this reason if no other the test should be continued. 
It is not uncommon for a stone to be so situated in a build- 
ing that it must sustain a heavy load. In very large buildings 
single columns and blocks are often required to carry huge 
masses of superstructure. Bridge trusses are often supported on 
blocks of stone which sustain the combined weight of the super- 
structure. Before using a stone for any of these purposes it is 
well to know with a fair degree of accuracy its crushing 
strength. 
The pressure exerted on the stone in the lower courses of a 
building of ordinary dimensions is not very great. It has been 
computed that the stone at the base of Washington monument 
sustains a maximum pressure of 22.658 tons per square foot, or 
314.6 pounds per square inch. Most architects require a stone 
to withstand twenty times the pressure to which it will be sub- 
jected in the wall. This factor of safety, however, would only 
require a crushing strength of 6292 pounds per square inch for 
stone at the base of the Washington monument. The pressure 
at the base of the tallest buildings yet constructed in this coun- 
try can scarcely exceed one half that at the base of this monu- 
ment, or 157.3 pounds per square inch. With a factor of safety 
of twenty the stone used in such positions must have a crushing 
strength of 3146 pounds per square inch. There are very few 
