XXIV. W. H. WARREN. 
dbs ily 
oe Ge 
We have— 
z= 8 a 
Alo 
But wats is proportional to the diameters in circular sections, 
and to the ratio of b to ¢ in rectangular sections, hence we have 
the following proportions :—. 
Circular Sections— 
Diameter ‘ ..d=0°3"” 0:4” 0:5” 0:6” 0-7” 0:8" 10° 
Useful length twee 
reference points ..2= 3” 4” 5” 6” 7 8 10° 
Rectangular Sections— 
Ratio b tot. ... Pal0- 16 80 95 3 ae 
Useful length ee BO OT SO ee 
Compare these results with Plate 1, figs. 1 to 7. 
CoMPRESSION. 
For the determination of the elastic limits and yield point the 
French Commission recommend a diameter of 27:5 mm. (600mm* 
in cross section) with 100 mm. of useful length. The American 
Society suggest that the length should be from 10 to 20 diameters. 
For the resistance to crushing the French Commission suggest 
cubes or short prisms 25 mm. side, and the American Society 
cylinders 1” in diameter and 2” high. 
In regard to the test of long pieces which fail by buckling, the 
Commission recommend that the rativ of length of the test piece 
to the minimum radius of gyration should be constant, and they _ 
propose a value which shall be multiples of 5 or 10, Plate 1, figs- 
7 and 8. They recommend that the tests shall be made under 
well defined conditions, either complete clamping or perfect hing- 
ing. It appears to be preferable to adopt the latter method as 
clamping is unsatisfactory. 
Prof. Bauschinger has expressed the compression strength of @ 
test piece by the formula— 
