The strength of these may be ascertained by the same rule as that of square columns. The smallest width being taken in calculating the proportion of height to width, while the longest side must be taken into consideration in calculating the proportion of thickness to width.

Column 10 feet O inches long.

Size.

Thick-

Proportion of

Thickness to greatest Width.

Proportion of length to least

Width.

Actual Breaking weight Tons per sq. in. of Section.

8 in. X 4 in.

•06

1/133

30 to 1

6.78

BOUND COLUMNS OF PLATE IRON RIVETED.

Columns lO feet 0 inches long.

Same Columns Reduced in l.ength.

Diameter.

Thick-ness.

Proportion or thick-ness to

Diameter.

Proportion of length to Diameter.

Breaking Weight.

Tons per sq. inch.

Break In* Weight*. Tons per square inch.

5 ft. 0 in. long.

2 ft. 6 in. long.

1½

1

1/15

80 to 1

6.5

13.9

5.8

2

1

1/20

60 to 1

10.35

14.8

16.5

2½

•1

1/25

48 to 1

13.3

15.6

16.3

2½

•24

1/11

48 to 1

9.6

15.6

16.

2½

•21

1/12

48 to 1

9.9

13.

17.

3

•15

1/26

40 to 1

12.36

13.

16.5

4

•15

1/26

30 to 1

12.34

13.

6

•1

1/60

20 to 1

15.

17.

18.6

6

•18

1/46

20 to 1

18.6

It would seem from this that a thickness of 1/48. or ¼ inch in thickness for every foot in diameter is a good proportion for this kind of column.

It will be seen from these experiments, that it is the proportion of thickness to the width of cell which regulates the strength within certain limits of height.

And that a thickness of 1/30 or 1/8 inch for every 4 inches in width will give the highest result practicable for square columns.