Diameter.

Relative Hardness of American Woods.

If we take Shell-bark Hickory and assume a value of 100 for it, other woods will compare with it in hardness as follows:

Length of
1 lb. in inches.

Lengths of Round and Square Cast Iron Sash Weights.

To obtain the length of the weight, multiply the length of one

pound in inches by the number of pounds which the weight is to balance.

Length of

lb. in inches.

Window Glass.

Number of panes per 50 feet or in one box.

Weight of Skylight and Floor Glass per Square Foot.

BUILDING MATERIALS.

Corrugated and Galvanized Iron.

Corrugated iron forms an effective covering for the roofs and sides of buildings. For roofs it is usually laid upon the purlins and secured in place by clips of hoop iron bent around the purlins and riveted to the sheets at about 12 inches apart, taking special care to fasten well the projecting edges of the sheets at the eaves and gable ends of the roof to prevent the wind from loosening and folding them up. The sides of the buildings may be covered directly on the uprights or secured to sheathing. The corrugations vary in size; the smaller giving a more desirable effect, except in the case of very large buildings, where the larger is used, being stiffer and admitting of greater span. Nos. 20 and 22 for both roofing and siding are those more generally used. The result of transverse strain tests on a No. 20 corrugated sheet 2' 0" wide, 6' 0" long between supports, loaded uniformly with fire clay, was as follows:

Load per Square Foot. Deflection at Center Permanent Deflec

Lbs.

under Load.

Inches.

tion. Load Removed.

WEIGHTS OF SHEET IRON, FLAT AND CORRUGATED. CALCULATED FOR FLAT SHEETS 30% INCHES WIDE.

Safe Loads in Tons of 2,000 lbs. for Hollow Cylindrical Cast Iron Columns. th of the Ultimate Strength.

Tons. Tons. Tons. Tons. Tons. Tons. Tons. Tons. Tons.

88.0 82.3 76.2 70.0 64.1 58.4 53.2 48.4 44.1
106.6 99.6 92.2 84.8 77.6 70.8 64.4
101.4 95.9 89.8 83.6 77.4 71.5
143.7 135.8 127.3 118.5 109.7 101.2
162.7 153.8 144.1 134.1 124.2 114.6 105.5
114.8 109.4 103.5 79.3 91.0 84.8
139.9 133.3 126 1 118.6 110.9 103.3 97.8
185.7 177.1 167.5 157.5 147.3 137.2 129.8 118.3 109.5
128.0 122.9 117.2 111.0 104.7 98.4 92.2 86.1
156.4 150.1 143.1 135.7 127.9 120.2 112.6 105.2
183.3 175.9 167.7 159.0 149.9 140.9 132.0 123 3
232.7 223.4 213.0 201.9 190.4 178.9 167.6 156.6 116.1
141.2 136.3 130.7 124.7 118.5 112.1 105.8 99.5 93.5
172.8 166.8 160.0 152.7 145.0 137.2 129.4 121.8 114 4
258.9 249 9 239.7 228.7 217.3 205.5 193.9 182 5 171.3
154.3 149.6 144.3 138.5 132.3 125.9 119 5 113.1 106.8

25.1

78.40

58.7 53.4

30.4

94.94

60.5 55.5

28.3

88.23

85.6

78.7

40.1

124.99

97.0 89.1

45.4

141.65

73.1

67.7

31.4

98.03