yield can only be applied to the burning of lime: these are called stinking coals. The first coal forms the ninth bed from the surface, at the depth of one hundred and two feet, and is not more than four inches thick: it is very sulphurous. In the space between this and three hundred and ninety-six feet, lie nine other beds of stinking coal, none of which exceeds the thickness of seven inches except the lowest, which is a little more than a foot and a half thick. The first bed that is worked is a live-foot coal at the depth of four hundred and ninety feet, between which and the big-flint sandstone, already mentioned, are a ten-inch and a yard coal.
But the greatest deposit of coal is in the space (about one hundred feet) between the big and little flints, consisting of nine beds, the aggregate thickness of which is about sixteen feet. Beneath this, and the lowest bed of the whole formation, is a sulphurous eight-inch coal.
The depths and thicknesses mentioned above are such as present themselves in the meadow pit in Madeley colliery, which from its offering a greater number of strata than are to be found in any other pit, deserves to be considered as the best authority for the whole coal field, as far as regards the number and order of the beds of which it is composed. But, by consulting the registers of the other collieries, we learn, that some of the strata composing this formation, especially the beds of coal and clay, are by no means so regular, either in their extent or thickness, as is generally represented to be the case with stratiform floetz rocks.
Thus, if we confine our attention only to those beds which lie between the big and little flints, and which constitute by far the most regular part of this coal field, we shall find that the penny stone bed, which in the Madeley pit varies in thickness from six to eight feet, is fifteen feet thick at Lightmoor, about twenty feet at Dawley,
