1302
THEORY AND PRACTICE OF ENGINEERING.
Cook II.
In the foregoing tables the primitive horizontal strength of oak is considered as 1000,its vertical strength at 807, and its cohesive or absolute strength at 1821 : for its appli-cation to the other species of timber the following table has been calculated : —
Primitive or.
Primitive
Vertical
Strength.
Strength.
Apricot
1096
1255
2040
Acacia, yellow
-
-
-
-
780
1228
1560
Arbutus
-
-
-
-
857
1062
1620
Alder
-
-
644
780
20S0
Ash
-
-
-
-
1072
1112
1800
Apple
.
-
-
-
976
903
1187
Aspen
-
-
-
624
717
1293
Birch
-
-
-
-
853
861
1980
Box
-
-
-
1160
1444
2324
Beech
.
.
-
_
1032
986
2480
Cedar
.
-
-
_
627
720
1740
Cherry
.
-
961
986
1912
Chestnut
-
-
_
957
950
1944
- horse
-
►
-
.
931
689
1231
Citron
-
-
-
.
1192
871
1460
Cypress
-
-
-
682
869
1880
Ebony
-
-
-
1155
1062
2321
Elder
-
-
-
1072
789
1500
Elm
-
-
-
-
1077
1075
1980
Fir
-
-
.
-
918
851
1250
Lemon
-
-
-
1087
858
1400
Larch
-
-
-
.
843
902
1460
Lignum vita?
-
-
-
.
707
741
1113
Lime
-
-
_
.
750
717
1407
Maple, foreign
-
-
-
-
1094
843
2094
Mulberry
-
-
-
-
981
1031
1050
Oak
.
-
.
1000
807
1821
Orange
-
.
-
.
1180
843
2340
Pine tree
•
.
.
_
882
804
1041
Plane
-
-
.
_
728
830
1916
-, Oriental
-
.
.
776
874
931
-, Occidental
.
-
_
853
941
1031
Poplar
.
.
-
.
586
680
940
Plum
-
.
.
_
950
843
1770
Pear
-
.
.
850
816
1680
Sycamore
-
-
-
_
900
968
1564
Service
-
-
965
981
1642
Tulip tree -
-
-
.
-
563
682
981
"Walnut
-
-
-
900
733
1120
-, American
-
-
-
.
864
701
1020
Yew
-
-
-
-
1037
1375
2287
This is deduced from pieces 19*188 lines English square.
When a piece of timber is put in an upright position, it seems at first that it will carrythe same weight, whatever may be its length; but experience shows us that when a postis more than seven or eight times the width of its base in height, it bends under theweight, previous to crushing or giving way. When a post is 100 times its diameter, it isincapable of maintaining an upright position, and then we find its strength diminishes inrelation to the height: to crush a piece of oak which is too short to bend, it requires 49-72pounds avoirdupois for every -Jjjjgj area of an inch at its base, and for fir timber 56-16 pounds.
Rondelet used cubes of oak and fir in the experiments he made, and found they diminishedin height by compression previous to disuniting, the first more than a third, the latter ahalf: when either of these timbers are of a length to bend under the weight imposedupon them, they immediately have their strength diminished, and he found the meanstrength of oak to be 47*52 pounds avoirdupois for a cube of of an inch, which isreduced to 2-16 pounds, when the height is as much as 72 times the width of the base:for a cube whose height was 1, the strength was taken as 1; for a post equal to 12times its base, the strength was five-sixths; for 24 times, a half only ; for 36 times, a third}