30 Mr. N. J. Winch on the Geology of 



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 sand- 

 stone 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 neighbour- 

 hood 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. 



