sections of Hebburn and of Sheriff hill, as exhibiting when taken in succession, a series of Coal measures of the thickness of about 270 fathoms. In the former colliery are the beds which lie above the High Main coal; in the latter principally those which lie beneath it; together they present the entire order of the coal seams, that are best understood in the Newcastle district: but it will be seen even in these two examples, what want of agreement there is in the beds which lie in the two sections above the High Main coal.
The most valuable seam in the whole Coalfield in point of thickness and quality is that called the High Main, of the mines situated between Newcastle and Shields. It there averages above 6 feet from the roof to the floor, contains a large proportion of bitumen, and is sufficiently hard to bear carriage without breaking into very small fragments. From this the owners of Old Byker, Byker St. Anthony's, Walker, Walker Hill, Willington, Old Benton, and Flatworth mines, formerly drew their riches; and it continues to supply the present proprietors of Hartley, Blyth, and Cowpen, north of the 90 fathom Dyke; of Heaton, Bigge's Main, Wall's End, Pevey Main, Collingwood Main, and Marton Collieries on the north side of the Tyne, and of Hebburn, Jarrow, and Manor's Wall's End, on the south side of that river. I have already described in part the basseting of this coal seam along the course of an oval line, of which Jarrow is the centre; from which some idea may be formed of the extent of country which it underlies north of the 90 fathom Dyke. At a land-sale pit, a little above the Ouse burn Bridge, near Newcastle, this seam was found at 14 fathoms; but on the Town-moor, from the numerous vestiges of ancient pits, it appears to be exhausted.
The lower seams under the same lands are without doubt untouched. Wallis, in the history of Northumberland, gives an account of a fire happening in the High Main coal, about 140 years
