85
TENSION.
Modulus of frac-ture or length of
Weight
lbs. avoirdupois
a rod one quar-
Material.
of a cubic
required to
ter of an inch
draw asunder a
square in section
ounces.
bar six inches
of the material
long \ of an
equal in weight
inch square.
to the tensileweight.
-
Cast iron bar, horizontal -
-
7113
1166
6043
Ditto vertical
-
7074
1218
6347
Hard gun-metal, mean of twotrials - - - f
7033
2273
11914
Cast steel previously tilted
-
7113
8391
43492
Cast copper
-
8788
1192
5000
Fine yellow brass
-
8396
1123
4931
Cast tin
-
7291
296
1497
Cast lead
-
11352
114
370
English iron reducedper hammer I
7788
f 3492
16529
-J
\ 4504
21319
Shear steel ditto ditto
-\
7840
/ 7977
37508
Blister steel ditto ditto
18322
39131
Wrought copper ditto ditto
8879
2112
8769
Rondelet, page 208. Vol. I. has given a table, in which is indicatedthe specific gravity, weight per foot cube, and weight required to crush acube of 25 centemetres base, and one 4 inches base of 180 different kindsof stone, and of 18 different kinds ofBasaltes, porphyries, granites, anddifferent kinds of marbles.
He observes, that the heaviest stones are not the strongest. With anequal or less specific gravity, those of the finest grain, most compact tex-ture, and deepest colours, will support the greatest weight. The strengthof ordinary stones of the same kind, colour, and grain, augments with thespecific gravity. He says, page 97. Vol. III. All these experiments provethat the strength of stone, of the same nature and form, increases verynearly in the ratio of the area of its base. Gauthey, Vol. I. page 275 and276, says, the results reported by M. Rondelet, agree in general withmine, (see table 4, Gauthey, Vol. I.) and that it is convenient and safe inthe application to assume, that it does so increase.
Mr. George Rennie, page 132. Phil. Trans. 1818. remarks, “ In ob-serving the results presented by the preceding table, it will be seenthat little dependence can be placed on the specific gravities of stones,so far as regards their repulsive powers, although their increase is cer-tainly in favour of their specific gravities. But there would appear to besome undefined law in the connection of bodies with which the specificgravity has little to do. Thus statuary marble has a specific gravity aboveAberdeen granite, yet a repulsive power not much above half the latter.Again hardness is not altogether a characteristic of strength, inasmuch asthe limestones which yield readily to the scratch, have nevertheless a re-pulsive power approaching to granite itself.
It is a curious fact, in the rupture of amorphous stones, that pyramids