344 SAW OES ID ON SIYLOIGIN TiS) 
building stones in the country that do not have a higher crush- 
ing strength. It may happen, however, that owing to an unequal 
distribution of the load certain stones in the wall or columns, 
will be called upon to sustain twenty, or even fifty times the 
natural load, in which case the crushing strength should be much 
greater. All things considered, however, a crushing strength of 
5000 pounds per square inch is considered sufficient for all ordi- 
nary building constructions. 
The crushing strength of a stone can be obtained quickly 
and accurately in any laboratory which is provided with appli- 
ances for cutting and dressing stone cubes and a testing machine, 
for determining the compressive strength. The cubes to be 
tested should measure uniformly 2 X 2 X 2 inches, this being 
generally conceded to be the standard size. Smaller or larger 
cubes may be used, but some authors, following the early experi- 
ments of General Gilmore, still maintain that the crushing 
strength per unit of area varies with the size of the cube tested. 
Believing this, General Gilmore constructed an empirical formula 
for the purpose of reducing all tests to pounds per square inch 
on two-inch cubes. However, it has been shown to the satisfac- 
tion of most persons, that this formula is neither theoretically 
nor practically true. It is now believed quite generally that the 
crushing strength per square inch is the same whether the cubes 
tested be large or small; cubical or prismatic in shape. Until 
this question is settled to the satisfaction of all it is best that all 
tests be made upon two-inch cubes. 
The cubes should be very carefully sawed from stone which 
has not been injured by rough handling or hammer dressing. 
The faces should be rubbed smooth, and the opposite sides 
should be made parallel. Before the cubes are placed in the 
testing machine they should be thoroughly dried and the average 
area of the bearing faces determined. Thin strips of blotting 
paper, wood, or lead, are often placed between the steel plates 
of the machine and the bearing faces of the stone cubes, to 
assist in distributing the load. It is claimed by some, however, 
that this has a tendency to lower the crushing strength. The 
