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



vein, it appears to be divided into a number of small branches, 

 some of which are upcasts and some downcasts, which break and 

 rend the coal-measures to the width of 200 yards. In the Wear 

 water mines it is an upcast on the northern side of 30 fathoms. 



The Thistle pit dyke which is a downcast of eight fathoms to 

 the south, and traverses the Coal-field from west to east, appears 

 to have been as well known to the miners who lived nearly a cen- 

 tury since, as to those of the present day. It was the southern 

 limit of the ancient colliery situated at Heaton and Benton banks, 

 and by perforating it the mine at Heaton was inundated on the 3d 

 of May, 1815, when the viewer and seventy-four men and boys 

 lost their lives. — For an account of this catastrophe, see Monthly 

 Magazine and Philosophical Journal. 



The Heworth dyke is an upcast on the southern side of 25 

 fathoms, and from the vicinity of Falling hall it stretches towards 

 the west, and enters the main dyke at Ryton. The high-main coal 

 to the south of this dyke is said to lose a strong parting known by 

 the name of Heworth band. 



At Hebburn, Oxclose, Ravensworth, Lambton, Newbottle, Lum- 

 ley, Raynton, and every other colliery worked in the district, simi- 

 lar dykes occur ; and, following the same law as the veins of the 

 Lead-mine district, they elevate the strata on that side towards 

 which they dip. 



Whatever be the throw or difference of level occasioned in the 

 coal-measures by these dykes, it never happens, as might be expected, 

 that a precipitous face of rock is left on the elevated side ; or that 

 the lower side is covered by an alluvial deposit, which connects the 

 inequality of the beds that are in situ ; but the surface of the ground 

 covering the vein is rendered level by the absolute removal of the 

 rocky strata on the elevated side. The same phenomena have been 



