A HISTORY OF DURHAM 



peroxide of iron by the process of weathering. 

 Both the brown hematites so formed and the 

 original spathic ores have been mined, and have 

 laid the foundation of an iron industry in that 

 part of the county. The ores are nowadays 

 barely worth working, and the amount of iron 

 so raised is unimportant, but the ironworks 

 originally founded to treat them survive in the 

 form of important iron and steel-works, treating 

 ores imported from the neighbouring counties or 

 from abroad. 



Directly above the Mountain Limestone Series 

 comes the Millstone Grit, which forms an irregular 

 belt about five miles wide, running, roughly 

 speaking, north and south across the county. 

 This formation contains but little workable 

 mineral ; some thin and usually unprofitable beds 

 of coal occur in it, but they are of no practical 

 importance. In the overlying Lower Coal 

 Measures, which pass gradually into the Coal 

 Measures proper, a bed of ironstone exists, a little 

 below the Brockwell seam, and was for some 

 time worked in the Derwent valley, its outcrop 

 having been exposed in the valley of that river. 

 This ironstone has not been worked for over half 

 a century, but was the material from which 

 sword-blades were made by German workmen, 

 in the valley of the Derwent, a locality which at 

 one time enjoyed a high reputation for this craft. 

 The well-known Consett Iron Works (first 

 known as the Derwent Iron Works) were 

 founded originally to smelt these ores, and still 

 exist as flourishing iron and steel-works, although 

 not a pound of ore is mined in the district, the 

 whole of the ores there smelted being imported 

 from abroad. 



The greater portion of the north-eastern part 

 of the county of Durham consists of true Coal 

 Measures, within which numerous seams of coal 

 are known. Some fifteen different workable 

 seams are known to exist, with a total thickness 

 of about 40 ft. of coal. In the southern and 

 eastern portion of the county the denuded Coal 

 Measures dip underneath the unconformable 

 overlying Permo-Triassic rocks, but still exist at 

 a depth which admits of their being worked to 

 advantage. The area of exposed Coal Measures 

 is probably about 250 square miles, whilst the 

 coalfield continues underneath the newer rocks 

 for a further area of about 200 square miles. 

 Furthermore, it must be borne in mind that the 

 coalfield is not bounded by the sea-shore, but 

 exists underneath the sea, and is in places already 

 worked there. It is generally supposed that it 

 may be workable for a total distance of ten miles 

 beyond the shore-line. Upon this basis the 

 recent 1903 Coal Commission estimated that 

 there were 4,401 million tons of coal remaining 

 to be worked in the Coal Measures of the county 

 of Durham up to the shore limit, and a further 

 870 million tons of coal could be won underneath 

 the sea, making the total amount of coal capable 



of being won in the county of Durham 5>27i 

 million tons. The Permo-Triassic rocks overlie 

 the Coal Measures quite unconformably, there 

 being evidence of considerable erosion of the 

 upper portions of these Measures before the newer 

 rocks were deposited. The lower member of 

 the latter consists of a bed of yellow sand carrying 

 an enormous quantity of water, which has proved 

 to be one of the most serious obstacles to the 

 working of the Coal Measures beneath these newer 

 rocks. Thus in the magnificent sinking recently 

 completed at Horden, Seaham Harbour, close 

 upon 10,000 gallons of water had to be pumped 

 per minute during the course of the sinking. 

 Above this sand comes the Magnesian Limestone, 

 which is frequently extensively fissured, and 

 carries also very large bodies of water. This 

 Magnesian Limestone is extensively quarried, but 

 otherwise contains no minerals of commercial 

 importance, although small lead-veins are known 

 in it, and veins of copper have been met witli in 

 the quarries at Raceby Hill and Garmondsway, 

 but not in workable quantities. The overlying 

 or so-called Red Beds developed in the southern 

 portion of the county are frequently known as 

 the Salt Beds on account of their containing thick 

 layers of rock-salt and gypsum, which have given 

 rise to an important salt-producing industry in 

 the neighbourhood of the River Tees. 



It is scarcely possible to write an account of 

 mining in the county of Durham without 

 continual reference to the operations going 

 on in the adjoining counties, because neither 

 geological structures nor mineral deposits are 

 respecters of county boundaries. In coal-mining 

 the question is further complicated by the facts 

 that not only does the great northern coalfield 

 extend over the adjacent counties of Northumber- 

 land and Durham, but that the principal coal- 

 exporting port, namely the River Tyne, is 

 common to these two adjacent counties ; and, 

 furthermore, the districts assigned to the Inspectors 

 of Mines coincide neither with county boundaries 

 nor geological structures. Such a history must 

 in fact be the history of a coalfield and not that 

 of the county or counties within which it may 

 happen to lie ; hence, this article, especially in 

 as far as it relates to coal, must be read in con- 

 junction with that of the history of coal-mining 

 in Northumberland. 



COAL 



Although lead ore has long been mined in 

 the hilly district that forms the western portion 

 of Durham, and although iron ore has been 

 worked in several places within the county, these 

 branches of the mining industry are reduced to 

 utter insignificance in comparison with the enor- 

 mous development of coal-mining, which may be 

 said now to form the staple industry of Durham. 



Here, as elsewhere, the origin of coal-mining 

 is lost in obscurity, and it is quite uncertain when 



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