| Bottom Edge. | Top Edge. | |||||
| Expan- sion. | Percentage on original length. | Contrac- tion. | Percentage on original length. | |||
| Inches. | Inches. | |||||
| After | 1st | cooling | .05 | .18 | .26 | .91 |
| „ | 2nd | „ | .10 | .35 | .43 | 1.51 |
| „ | 3rd | „ | .10 | .35 | .54 | 1.90 |
| „ | 4th | „ | .14 | .49 | .75 | 2.64 |
| „ | 5th | „ | .20 | .70 | .92 | 3.24 |
| „ | 6th | „ | .30 | 1.05 | 1.25 | 4.40 |
| „ | 7th | „ | .34 | 1.20 | 1.50 | 5.28 |
| „ | 8th | „ | .38 | 1.34 | 1.56 | 5.53 |
| „ | 9th | „ | .39 | 1.37 | 1.66 | 5.84 |
| „ | 10th | „ | .40 | 1.40 | 1.76 | 6.19 |
| „ | 11th | „ | .41 | 1.43 | 1.84 | 6.48 |
| „ | 12th | „ | .44 | 1.55 | 1.96 | 6.90 |
“This was cooled half in air and half in water, and the length of the two edges measured accurately after each of twelve coolings. At the end of this experiment the air-cooled edge had contracted 6.9 per cent., while the water-cooled edge had expanded 1.55 per cent. of the original length. The effect on the bar was to make it gradually curve, the water-cooled or extended edge becoming convex, the air-cooled or contracted edge concave.
Fig. 1434.—Experiments with a wrought-iron bar. Appearance of the piece before heating.
Fig. 1435.—Appearance of the bar after the twelfth cooling.
