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The same quantity of metal in the feather-edged bar, was not so strong as in the four-inch bar.

The semi-elliptical bar exceeded the four-inch bar, although taken out of it. The parabolic bar came near it.

Observations by various Authors on the Strength of Materials.

360;

A wire of th of an inch of lead, breaks with 29 lbs., of tin, with 49 lbs.; of copper, with 2994; of brass, with of silver, with 370; of iron, with 450.-Emerson. A cylinder, an inch in diameter, will bear, when loaded to of its whole strength, if of fir, 8.8 cwt.; if of rope, 22 cwt.; if of iron, 135 cwt.-Emerson.

The cohesive strength of a cylinder of iron, an inch in diameter, is 63,466 or 63,173 pounds, the mean 63,320 pounds, which is 28 tons, 5 cwt. 1 qr. 12 lbs.—Rumford.

The comparative cohesive strength of gold, is as 150,955; of silver, 190,771; of platina, 262,361; of copper, 304,696; of soft iron, 362,927; of hard iron, 559,880.-Sickengen. The hardness of metals follows this order,-iron, platina, copper, silver, gold, tin, lead.-Cavallo.

In general, iron is about four times as strong as oak, and six times as strong as deal.—Banks.

Wood is from 7 to 20 times weaker transversely than longitudinally. It becomes stronger both ways when dry.

A piece of sound oak, an inch square, bears 8000 pounds directly, and is broken transversely by 200, at the distance of 12 inches from the fulcrum.-Robison.

The immediate transverse strength of lateral adhesion of most substances exceeds their direct cohesive strength, but the difference is less in fibrous substances than in others.-Robison.

The strongest form of a substance included by horizontal surfaces, for supporting a weight at its extremity, is that of a triangle. The same form is also the stiffest.Emerson.

For supporting a weight distributed uniformly throughout its length, the form must be that of a parabola.— Emerson.

A triangular prism fixed at one end, with its edge uppermost, is weaker than if its depth were reduced to eightninths, by cutting away the edge.-Emerson.

If a piece be sliced in a divided beam, equal in depth to half the depth of the beam, the strength is greater than that of the entire beam, in the ratio of 1 to 1.054, very nearly.-Robison.

A mortise-hole should be taken out of the middle of a beam, not from one side; but if it be on the concave side, and fitted up with hard wood, it does not diminish the strength.-Emerson.

If a cylinder is to be supported at two points with the least strain, the distance between the points should be .5858 of the length.-Emerson.

A soft iron bar, a spring tempered, and a hard one, were bent to equal angles by five pounds; with six, the hard bar broke; with seven, the soft one bent, but returned as far from its new position, upon the removal of the weight, as if it had not been bent. The elastic bar was broken by 18 pounds.- Coulumb.

Weight of one Foot in length of flat Bar-iron.

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Broad Thick Weight in Broad Thick, Weight in Broad Thick Weight in

4 lach

pounds.

pounds.

pounds.

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Weight of one Foot in length of Wrought-iron.

ibs. inch.

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0.21 13

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0.16 13

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Weight of Cast-iron Plates per foot superficial, of the fol

lowing thicknesses.

Thickness

Weight

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lb oz lb 02 18 oz lb oz lb 02 lb 02 lb ΟΙ lb 0% 4 139 1014 819 524 229 0 33 13 38 10

Weight of Sheet Lead per foot superficial, of the following

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Weight.. 356 7 10 12 142 19 2944 59 lbs.

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