mentioned is really not borne out by the facts as to all places, may be shown by the following deductions from the pit sections furnished me in the district.
In six shafts in the Stow Heath colliery, partly in the occupation of Messrs. Sparrow, partly of Messrs. Ward, we find the following values for the thickness of the "green rock," and for the thickness of the whole measures, including the " green rock," from the top of the New mine coal to the top of the Blue flats ironstone:-—
| Pit. | Green rock. | Total beds from New mine coal to Blue flats. |
| FT. | FT. | |
| 1. | 30 | 164 |
| 2. | 33 | 157 |
| 3. | 51 | 205 |
| 4. | 55 | 177 |
| 5. | 66 | 204 |
| 6. | 66 | 214 |
which shows that the total thickness does increase with the increase of the thickness of "green rock," although not regularly or in strict proportion, owing to the original irregularity in the thickness of the other measures.
In three pits at the Portobello colliery, just where the "hole" of "Moseley Hole," is engraved in the map, all three pits being within a distance of 264 yards, we get the following thicknesses:—
| Pit. | Green rock. | Total beds from New mine coal to Blue flats. |
| FT. | FT. | |
| 1. | 59 | 168 |
| 2. | 56 | 104 |
| 3. | 84 | 190 |
In which we find the increase in the total thickness to be very nearly in direct proportion to that of the green rock.[1]
In an open work in the New mine coal, some years ago, on Wednesfield Heath, a dyke of the white feldspathic-looking trap was seen cutting up into the coal from below, and ending in some black shale. In some quarries north of Willenhall the same rock may still be seen in veins cutting through the Coal-measures.
In the northern portion of the coal-field, north of Wednesfield, and Walsall, no trap rock is known to show itself at the surface of the ground, with the exception of a little spot of hard dark hornblendic trap at the Essington wood brick-kiln, only to be seen in a small quarry partially concealed by underwood, and surrounded by the red clays of the upper Coal-measures.
Much "green rock" was found in some old sinkings between Pool Hayes and the New Invention, obliging the works to be abandoned. I was informed that in some sinkings made by Colonel Vernon two or three miles north of Bloxwich on Essington Wood, the measures were found to be disturbed and altered by "white rock trap," to such an extent as to oblige them to abandon the undertaking. Large intrusive
- ↑ I have insisted a little more strongly on this point than its real importance deserves, because it is a good illustration of the error into which purely practical men are so apt to fall, that, namely, of over-hasty generalisation from insufficient data. The charge of "theorising," as it is called, is so often brought as a criminal charge against scientific men, that it is but fair to show those instances in which theory necessarily leads to truth, and therefore to safety, in order to counterbalance those in which it may occasionally have led to danger or expense.
