Or an average of 12 feet a day.
In Coal measures:
| A depth of | 1008 | feet in | 146 | days |
| 802 | ” | 168 | ” | |
| 700 | ” | 48 | ” | |
| 558 | ” | 42 | ” |
Or an average of 7½ feet a day.
TIMBER.
To find Solidity of Round Timber.
When all dimensions are in feet: Length × (¼ mean girth)² = cubic feet.
When length in feet, girth in inches: Length × (¼ mean girth) ÷ 144 = cubic feet.
When all dimensions are in inches: Length × (¼ mean girth)² ÷ 1728 = cubic feet.
To find Solidity of Square Timber.