Fig. 1429.
“Experiment No. 6.—Wrought-iron plate, .74 inch thick, planed on both surfaces and all edges to a form nearly rectangular, and of the dimensions given in [Fig. 1429].
“Specific Gravity.—Two small samples were cut out of different parts of the same piece of plate from which the experimental piece was planed, and the specific gravity determined as follows:—
| No. 1 piece | 7.629 | } | Mean, 7.64. |
| No. 2 piece | 7.651 |
“Quality.—Subjecting a piece to tensile strain in the direction of the grain, it broke at 21.2 tons per square inch of section, the ductility being such that an elongation of 8.3 per cent. occurred before fracture, with a reduction of 9.6 per cent. of the area of fracture. This may be looked upon as representing a fairly good quality of iron.
“A bar of wrought iron, 11⁄8 inches square and 30.00 inches long, was heated to redness, and then allowed to cool gradually in air. Measurements after each of five coolings showed no perceptible change of length.
“Experiment No. 4.—Wrought-iron bar, 11⁄8 inches square by 30 inches long, heated to a white heat and cooling gradually in air.
| Contraction. | Percentage on original length. | Remarks. | |||
| Inches. | |||||
| After | 1st | cooling | No change. | —— | |
| „ | 2nd | „ | „ | —— | |
| „ | 3rd | „ | .02 | .07 | —— |
| „ | 4th | „ | .05 | .17 | —— |
| „ | 5th | „ | .05 | .17 | —— |