and which sometimes do not descend lower than the upper seams of coal. These are called gashes by Williams, and washes by our miners: they are filled with water, clay, sand, and rounded sandstone pebbles similar to those in the beds of rivulets.
3. Basin-formed depressions in the floors of the mines, called swellies by the miners; by which the coal is considerably thickened, the roof of the seam preserving its regularity. These occur when the coal is nearly horizontal.
4. Nips, where the coal nearly disappears, the floor and the roof coming into contact. Near Fawlon Slate in the neighbourhood of Fenham, 80 acres of coal are said to be lost in this manner.
At Hetton and at Hebburn, and in other parts of the Coal-field, the coal-measures are covered by large tracts of quicksand, which appear to have been the beds of ancient lakes. Mr. Fenwick has lately penetrated through a most formidable obstruction of this kind at Hetton by means of a number of cast—iron cylinders.
Having now given a general account of the coal beds, and of the derangements to which they are subject, I proceed to the Colliery Sections, with which I commence on the northern side of the main dyke near the sea, and thence pass towards the west: then crossing to the southern side of the main dyke at Montagu colliery and returning to the east, I exhibit the strata pierced at some of the principal collieries on the Tyne, and the lower beds found at Gateshead Fell and on the Wear. Some other examples follow, which are taken from the western and south-western borders of the Coal-field.
