Ropes made of IRON WIRE are full three times stronger than those of hemp of equal circumference.

White ropes are found to be most durable. The best qualities of hemp are-1. pearl gray; 2. greenish; 3. yellow. A brown color has less strength.

THE BREAKING WEIGHT of a good hemp rope is 6400 lbs. per square inch, but no cordage may be counted on with safety as capable of sustaining a weight or strain above half that required to break it, and the weight of the rope itself should be included in the estimate.

THE RELIABLE STRENGTH of a good hemp cable, in pounds, is usually estimated as equal to the square of its circumference in inches by 120. That of rope X 200. Thus, a cable of 9 inches in circumference may be relied on as having a sustaining power = 9 X 9 X 120

9720 lbs.

THE WEIGHT, in pounds, of a cable laid rope, per linear foot, is the square of its circumference in inches X .036, very nearly.

The weight, in pounds, of a linear foot of manilla rope is the square of its circumference in inches X .03, very nearly. Thus, a manilla rope of three inches circumference weighs per linear foot 3 X 3 X .03 270 lbs., 316 feet per lb.

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CUSTOM HOUSE ALLOWANCES ON DUTIABLE GOODS. Draft, or Tret, is an allowance of weight for supposed waste on articles paying duty by the pound. It is deducted from the actual gross weight of the article, and is established as follows:

Tare is the weight-actual or assumed by law of the cask, sack, &c., in which the article paying duty is contained. It is deducted from the actual gross weight less the draft. The remainder is the net weight on which the duty is assessed, and the weight at which the heavy purchasers receive the goods.

Leakage is an allowance on the gauge of molasses, oils, wines, and all liquids in casks. It is established at 2 per cent., and is deducted from the actual gross gauge, less the real wants of the cask.

Breakage is an allowance of 10 per cent. on ale, beer and porter, in bottles, and 5 per cent. on all other liquors in bottles; or, if the importer prefer, the duties are assessed by actual count, he so electing at the time of making the entry. Common sized bottles are computed to contain 23 gallons per dozen.

Comparative Weight of Metals, Weight per Measure of Solidity, &c.

Exhibiting the Weight in pounds of One Foot in Length of Wrought or Rolled Iron of any size, (cross section,) from § inch to 12 inches,

To determine the weight, in pounds, of one foot in length, or of any length, of a bar of any of the following metals of form prescribed, of any size, multiply the weight in pounds, of an equal length of square rolled iron of the same size, (see table of square rolled iron,) if the weight be sought of

The weight of a bar of any metal, or other substance, of any given length, of a flat form, (and any other form may be included in the rule,) is readily obtained by multiplying its cubic contents (feet or inches) by the weight (pounds, ounces, or grains) of a cubic foot or inch of the article sought to be weighed; that is

Length breadth × thickness × weight per unity of measure. For the weight in pounds of a cubic foot or inch of different metals, see "TABLE of weights of metals per measure of solidity, &c."

OR, FOR FLAT OR SQUARE BAR,

Multiply the sectional area in inches by the length in feet, and that product, if the metal be

EXAMPLE. - Required the weight of a bar of steel, whose length is 7 feet, breadth 24 inches, and thickness of an inch.

2.5 X .75 X 7 X 3.4 = 44.625 lbs. Ans.

EXAMPLE.Required the weight of a cast iron beam, whose length is 14 feet, breadth 9 inches, and thickness 14 inch.

14 X 9 X 1.5 X 3.1287591.32 lbs. Ans.

TABLE,

Exhibiting the weight in pounds of One Foot in Length of Round Rolled Iron of any diameter, from inch to 12 inches.

To find the weight of an equilateral three-sided cast iron prism. width of side in inches2 X 1. 354 X length in feet = weight in lbs.

EXAMPLE.

A three-sided cast iron prism is 14 feet in length, and the width of each side is 6 inches; required the weight of the prism.

62 X 1.354 X 14= 682.4 lbs. Ans.

To find the weight of an equilateral rectangular cast iron prism.

9

width of side in inches x 3.128 x length in feet = weight in lbs.

To find the weight of an equilateral five-sided cast iron prism. width of side in inches2 5.381 X length in feet = weight in lbs.

To find the weight of an equilateral six-sided cast iron prism. width of side in inches2 X 8.128 X length in feet weight in lbs.

weight in lbs.

To find the weight of an equilateral eight-sided cast iron prism. width of side in inches2 × 15.1 × length in feet To find the weight of a cast iron cylinder. diameter in inches2 X 2.457 X length in feet In a quantity of cast iron weighing inches?

weight in lbs.

125 lbs., how many cubic

By tabular weight per cubic inch — 125.26073479.4 cubic inches. Ans.