The accompanying plan of the Great Northern Coal-field, in the counties of Northumberland and Durham, exhibits the relative position of the several collieries, and the ports at which their produce is shipped; also the cropping out of the coal measures, the magnesian limestone, and the new or upper and the old or lower red sandstone, as traced upon the surface from actual survey; the direction of the principal dykes or faults, by which the strata have been disjointed or broken; and the special districts wherein the various qualities of coal at present worked have been found in the greatest perfection.

This coal-field is geographically situated between 54° 35' and 55° 22' north latitude, and between 1° 10' and 1° 57' west longitude. Newcastle, the metropolis of the district, with its street architecture of beautiful freestone, is one of the finest towns in the kingdom, being in 54° 58' 30" north latitude, and nearly 1° 37' 30" west longitude. This district is bounded by the river Coquet on the north, and extends southward nearly to Hartlepool, near the Tees, a distance of about forty-eight miles. Its extreme breadth is about twenty-four miles, and its area has been calculated at not more than about 800 square miles. Mr. Hugh Taylor, in his evidence before a Parliamentary Committee, estimated the area at 837 square miles, or 535,680 acres; while Mr. R. C. Taylor, an American author, in his "Statistics of the Coal Trade," adopts an admeasurement of 780 square miles, or 499,200 acres. As representing the superficial area of the Great Northern Coal-field, either of the above admeasurements may be admitted; but if applied as the basis of a calculation for determining the quantity of what is termed the workable coal existing, and the probable period over which the supply will extend without being exhausted, both may be considered open to objections, and liable to redaction on several grounds, as will be satisfactorily shown in a subsequent portion of this paper. The writer, as the result of careful measurements, has adopted an admeasurement of little more than 700 square miles, or 448,000 acres, the details of which will be fully exhibited hereafter. In a considerable portion of the area southward, where the seams of coal are under the upper red sandstone, the magnesian limestone, and the lower red sandstone, they are proved so thin as to be almost unworkable.

The lineal boundaries of the Northern Coal-field assume the form of an irregular triangle, one side of which may be described as running from the mouth of the Tees westward to Woodland Colliery, near Cockfield, a distance of nearly thirty miles. The inland side is formed by the escarpment of the coal westward, and the line of sea-board may be adopted, with special modifications, as the boundary on the east, the junction northward being at a point near to Amble Harbour, at the mouth of the Coquet.

The general boundary, as thus described, is accurately defined upon the plan. Leaving the Tees near to Port Clarence, the boundary line on the south proceeds by the coast to Hartlepool, thence it follows the old Hartlepool Docks and Railway line, passing through Monkhesleton Dean, near to Castle Eden Pit, south of Hutton Henry. To make a straight line of boundary we may, perhaps, go not so far south as Wynyard or Newton Parks, thence on by Sheraton, Chilton, the Clarence Railway, to Middridge, East Thickley, Brusselton, south of Witton Park Iron Works, Evenwood, Norwood, Cowden, Cockfield Fell, Butterknowle, and Copley Dents, in the Township of Lynesack-cum-Softley, where it joins the extreme western boundary. The country beyond that point is mountainous and destitute of workable coal seams, but it abounds in rich limestone, iron and lead ores, which are extensively worked there and at Allenheads and Weardale.

After forming an angle at Copley Bents the boundary line proceeds in a northerly direction, with a slight inclination towards the east, in nearly a straight course to the Derwent, near to Hamsterley Hall, previous to which it crosses the river Wear below Wolsingham, where limestone, iron ore, and lend are met with; thence it proceeds towards Towlaw, a valuable ironstone district, where extensive iron works are established; next on to Thornley Colliery and Hedley Hope, and then to Consett, near Shotley Bridge, on the Derwent, at which place we meet with iron works on a scale of great and rapidly increasing magnitude.

The raw material for the works at Towlaw and Consett was principally supplied in the locality, but now immense quantities are brought from Cleveland at a cost of about 5s. per ton for carriage alone, and from other places. There are great facilities for the manufacture of iron at Consett, inasmuch as a very large capital is employed, and coal suitable for the purpose is obtained close at hand, and within twenty fathoms of the surface.

The coal seams "crop" out at Newland and many places along the hill towards the Derwent, putting in again towards the more elevated Crown Woods at Chopwell, Garesfield, Hedley, Stella, Towneley, and Mickley, and again cropping out west in the low lands near the Tyne, at Horsley Wood (near Wylam), and westward at Bywell. Thence, the course of the boundary is over Prestwick Carr, past Mitford (near Morpeth), towards the harbour of Amble-on-the-sea (near Warkworth), where the coal measures diverge from the land under the sea, before reaching which, the seams become very precarious in all directions.

The coal measures slope or dip from the out-crop towards the sea, from Widdrington Castle, on the north coast, to Castle Eden (near Hartlepool), in a south-easterly direction. On the west and north-west, they are bounded by the out-cropping of the underlying millstone grit and mountain limestone, which, in some cases, causes the coal to be found in patches, as at Shilbottle, Scremerston, Newton-on-the-Moor, and other places, such as North Tyne, Acomb, and Stublick.

The lowest working seams of coals are at Monkwearmouth pit, under the limestone, where the shaft, which is about one mile distant from and 100 feet above the level of the sea, has been sunk to the depth of nearly 1,700 feet to the Hutton seam, below which, as usual, will be found the Beaumont — Harvey or Towneley, Five-quarter, Stone Coal, Three-quarter, and Brockwell seams.

These seams have been worked in many of the westward collieries, for both sea and landsale use, and are considered to be the lowest workable seams of the coal formation.

The seams of coal south of Monkwearmouth (under the Hutton seam, which is the first workable one there), lie also at a considerable distance below the level of the sea. Westward near the Wear, at Pease's West Pits, the general out-crop of these seams is at a considerable height above the level of the sea. The same thing occurs near Wylam and Bywell on the Tyne. The inclination or rise of the coal measures westward is at the rate of 92 feet, or 15 fathoms per mile. In the mountain limestone, and in some places within the coal measures, westward, the iron and lead measures make their appearance.

Besides the general out-crop of the coal measures westward, several of the seams appear at the surface in the great valleys of the Tyne, the Derwent, the Team, the Wear, and the Tees, probably caused by denudation of the surface.