The following Table, showing the strength and weight of timber, is gleaned from the records of many experiments, chiefly those given by Hodgkinson, Tredgold, Barlow, Rankine, and Laslett. Some of these, in their turn, have embodied the results of experiments made by Buffon, Muschenhoek, Rondelet, etc.

It will be seen that the figures given vary throughout a very wide range. This is quite in accordance with practice.

Experiments made upon selected pieces of good quality show results differing greatly from one another, the difference being caused by variety in the age or state of dryness of the specimen, the size and form of the piece tested, the method in which the test has been applied, and the skill of the experimenter.

1 Britton.

Table Showing The "Weight, Strength, Etc., Of Various Woods

Wood seasoned.

Weight of a cubic foot

(dry).

Tenacity per sq. inch, lengthways of the grain.

Modulus of Rupture.

Modulus of Elasticity.

Resistance to

Crushing in direction of iibres.i

Comparative Stiffness and Strength, according to Tredgold. Oak being 100.2

Lbs.

Tons.

Lbs.

Lbs.

Tons per sq. inch.

StifT-ness.

Strength.

From

To

Moderately dry.

rhoroughly dry.

Acacia...

48

5.0

8.1

• ••

1,152,000 to

1,687,500

98

95

Alder ...

50

4.5

6.3

...

1,086,750

63

80

Ash, English..

43 to 53

1..8

7.6

12,000 to 14,000

1,525,500 to 2,290,000

3.8

4.2

89

119

„ Canadian..

30

2.45

10,050

1,380,000

2.5

77

79

Beech ...

43 to 53

21

6.6

9,000 to 12,000

1,350,000

3.4

4.2

77

103

Birch ...

45 to 49

6.7

11,700

1,645,000

1.5

2.8

Cedar ...

35 to 47

1,3

5.1

7,400 to 8,000

486,000

2.5

2.6

28

62

Chestnut..

35 to 41

4,5

5.8

10,660

1,140,000

67

89

Elm, English..

34 to 37

2,4

6.3

6,000 to 9,700

700,000 to 1,340,000

2.6

4.6

78

82

„ Canadian..

47

4.1

14,490

2,470,000

...

4.1

139

114

Fir, Spruce ...

29 to 32

1.3

4.5

9,900 to 12,300

1,400,000 to 1,800,000

2.9

3.0

72

86

„ Dantzic ...

36

1..

4.5

13,806

2,300,000

..

3.1

130

108

„ American red pine..

34

1.2

6.0

7,100 to 10,290

1,460,000 to 2,350,000

..

2.1

132

81

„ American yellow pine..

32

0.9

8,454

1,600,000 to 2,480,000

..

1.8

139

66

„ Memel ....

34

4.2

4.9

1,536,000 to 1,957,750

..

6

114

80

„ Kaurie ...

34

2.0

11,334

2,880,000

..

2.6

162

89

„ Pitch pine..

41 to 58

21

4.4

14,088 6,600 to

1,252,000 to 3,000,000

..

3.0

73

82

„ Riga..

34 to 47

1.8

5.5

9,450

1,328,000 to 3,000,000

...

2.1

62

83

Greenheart ...

58 to 72

3.9

4.1

16,500 to 27,500

1,700,000

5.8

6.8

98

165

Jarrah ...

63

1.3

10,800

1,187,000

..

3.2

67

85

Larch ...

32 to 38

1.9

5.3

5,000 to 10,000

1,360,000

..

2.6

79

103

Mahogany, Spanish

53

1.7

7.3

7,600

1,255,000 to 3,000,000

...

3.2

73

67

„ Honduras..

35

1.3

8.4

11,500 to 12,600

1,596,000 to 1,970,000

..

2.7

93

96

Mora ....

57 to 68

4.1

21,000 to 22,000

1,860,000

....

105

164

Oak, English..

49 to 58

3.4

8.8

10,000 to 13,600

1,200,000 to 1,750,000

2.9

4.5

100

100

„ American..

61

30

4.6

12,600

2,100,000

31

114

86

Plane ...

40

5.4

■ ••

1,343,250

78

92

Poplar...

23 to 26

2.68

.. .

763,000

1.4"

2.3

44

50

Sycamore...

36 to 43

4.3

5.8

9,600

1,040,000

3.1

82

111

Teak ....

41 to 52

1.47

67

12,000 to 19,000

2,167,000 to 2,414,000

2.3

5.4

126

109

Willow...

24 to 35

6.25

6,600

■ ■ •

1.3

2.7

..

...

Hornbeam .....

47-5

9.1

37

...

108

1 From Hodgkinson's experiments on short pillars 1 inch diameter, 2 inches high, flat ends, and Laslett's on 2-inch cubes.

2 This ratio is not always confirmed by the values of the moduli of elasticity as found by more recent experiments, and given in the fifth column of the above table.

Practical experiment upon material similar to that about to be used in any particular case is preferable to information extracted from tables; but if it is necessary to use the latter, the engineer should be inclined to credit his material with the lowest of the figures recorded, and then to apply a good factor of safety to cover defects in the pieces used, which defects may not have existed in the specimens experimented upon.

Mr. Hodgkinson found that timber when wet had not half the strength of the same timber when dry. This is an important point to consider in subaqueous structures.