1E+W+N.I.The area shall extend laterally on each side of (but not including) the inner area of protection to the following distance therefrom:—
| If the depth of the seam is 160 yards or under | Nil. |
| If the depth of the seam exceeds 160 yards, but does not exceed 170 yards | 1½ yards. |
| If the depth of the seam exceeds 170 yards, but does not exceed 180 yards | 2½ yards. |
| If the depth of the seam exceeds 180 yards, but does not exceed 190 yards | 4½yards. |
| If the depth of the seam exceeds 190 yards, but does not exceed 200 yards | 5½ yards. |
| If the depth of the seam exceeds 200 yards, but does not exceed 210 yards | 7 yards. |
| If the depth of the seam exceeds 210 yards, but does not exceed 220 yards | 8 yards. |
| If the depth of the seam exceeds 220 yards, but does not exceed 230 yards | 9 yards. |
| If the depth of the seam exceeds 230 yards, but does not exceed 240 yards | 9½ yards. |
| If the depth of the seam exceeds 240 yards, but does not exceed 250 yards | 10 yards. |
| If the depth of the seam exceeds 250 yards | To a line descending outwards from the railway or works at an angle of one horizontal to five vertical from a point on the boundary of the railway or works at rail level until the depth of 650 yards is reached and thence descending vertically. |