204 



DURHAM. 



Dwihan. tJie different implements tbuml in them, are supposed 



( ~~ ~"~ ** to have been wrought by tin- Komans. The lead mines, 

 * as has been already noticed, lie principally in 'l\ 



and Weardale. The ore is mostly found in veins. Where 

 the adjoining strata consist of limestone, the ore gene, 

 rally produces a considerable quantity of metal ; but 

 where the adjoining strata are freestone, indurated ar- 

 gillaceous earth, which are called here " plate beds," 

 there is little metal in proportion to the ore. Of the 

 different strata of limestone, that which is called " the 

 great limestone," and which i seventy feet thick, has 

 probably produced more ore than all the other strata 

 together. There are generally about eighty-six lead 

 mines wrought in this county : OT which, in ISO*), four 

 were in Derwent ; twenty in Wcardale on the north 

 side of the river, fourteen on the south side of the river ; 

 and forty-eight in Teesdale. The rent paid to the pro- 

 prietors is generally one-fitlh of the ore. The number 

 of people employed hns not been accurately ascertained. 

 Their earnings arc about L. 40 a-year on an average, 

 each man. Thirty-two cwt. of clean ore generally pro- 

 duces 20 cwt. of lead. The proportion of silver varies 

 much ; on the average, 22 ounces are produced from 

 each fother (22 cwt.) in Teesdale. If a ton will not 

 yield 8 ounces, it is not woi refining. In Derwent 

 there are four small mills, in Weardale three, and in 

 Teesdale five. In the parish of Middleton, which ex- 

 tends nearly twenty miles from west to east, and be- 

 tween two and three from north to south, nearly the 

 whole of the northern half is one series of lead mines. 

 As the district is very mountainous, the mode of clear- 

 ing them of water, called husking, is frequently practi- 

 sed. These " bushings" frequently raise.and discolour 

 the water of the Tees, destroying its fish in great quan- 

 tities. 



Irn ore. In the western parts of the coal district, great abun- 

 dance of iron ore is found ; and tradition reports, that 

 the Danes wrought it. It certainly appears to have 

 been smelted at some remote period, from the immense 

 heaps of iron slag which are found in various places. 

 They were certainly very regularly and extensively 

 wrought in the middle of the 14-th century. In the 

 lead-mine district, a few miles to the north of Stan- 

 hope, there is a large quarry, from which grey or free- 

 stone millstones, of a very superior quality, are pro- 

 cured. The bed of stone is 21 feet thick; but not 

 more than half of this consists of real millstone. A- 

 bove it lies a seam of finer freestone. About 40 mill- 

 ~ f ones are sold on an average in the course of the year. 

 What are generally called Newcastle grindstones are 

 got on Gatesheadfell in this county. They have been 

 wrought for a great number of years. Some are cut as 

 large as 76 inches in diameter, and 14 or 15 inches 

 thick. A cubic foot of them weighs 1 cwt. 1 qr. 14-lbs. 

 Five thousand chaldrons, each chaldron weighing 

 14 cwt. are made annually. In times of peace/ the 

 greatest demand for them is from Holland and France. 

 Of the various kinds of freestone found in different 

 parts of the county, that found at Heworth is most de- 

 serving of notice. It is of an open porous nature, and 

 stands the extreme heat of the glasshouse furnaces bet- 

 ter than any other stone or bricks. In the western 

 parts of Durham, grey slate for roofing is abundant. 

 What is called silver sand, and is used in the manufac- 

 ture of the finer kinds of glass, has been discovered 

 at Seaham. 



V.imettone. But next to coal and lead, limestone is the most abun- 

 dant in Durham. The positions and limits of the dif- 

 ferent limestone districts have already been pointed out. 



In Weardale, near Frosterly, a limestone is found that Durham. 

 t.ik< 's .1 line polish, and the colours are so beautifully > *~ P ~Y""* ' 

 variegated, that it is frequently used as marble for 

 chimney-piecea ; at i'ullison also, several strata of lime- 

 stone have been lately discovered, which approach still 

 nearer the quality of marble: they are clouded with 

 all the varieties of brown, from a dark brown to a 

 cream colour. This limestone takes a very fine polish, 

 stands any weather, and will not lly with* heat : there 

 are four strata ot'thi.- fine limestone, each three or four 

 indies thick ; they lie near the bottom of the quarry ; 

 above them is lime of the common quality. For the 

 purposes of agriculture, it has been found that the lime 

 from the quarries to the eastward of the coal district, 

 differ in their effects from the lime brought from the 

 quarries to the westward of this district : the former, 

 when laid on the land in heaps, and suffered to lie some 

 time before it is spread, renders the ground under it 

 unproductive ; and hence it is called, " burning lime ;" 

 whereas the other lime produces no such effect, and is 

 called " mild lime." These limes have been carefully 

 analyzed by Sir Humphry Davy and other chemists; 

 and the result is that the limestones to the east of the 

 coal district, that is, the hot or burning lime, contain a 

 large portion of magnesia ; ami those to the west of the 

 coal districts, called mild lime, are perfectly free from 

 magnesia. The purest of the mild limestone contains 

 <)()' of carbonate of lime, and only 4 of residuum ; and 

 the worst of the burning lime contains only 4t of car- 

 bonate of lime, 4-2 of carbonate of magnesia, and 14 of 

 residuum. The bad effects on the land were uniformly 

 found to be in proportion to the quantity- of magnesia 

 which each contained. According to Mr Marshall, the 

 limestone of Sunderland contains 97 of carbonate of 

 lime. This limestone is of a lightish grey colour ; the 

 rock near Sunderland, out of which it is wrought, is 

 upwards of .W feet high ; it is covered with 10 feet of 

 pale clay ; there are no regular seams ; but it is com- 

 posed of huge blocks; the interstices are filled with a 

 specie s of marl. 



About thirty years ago, a salt spring was discovered Salt spring, 

 in an engine pit, constructed for drawing water out of 

 the coal mines near Birtley. As it mixed with the 

 fresh water in the same pit, it would probably have re- 

 mained unnoticed, but for an accident which happened 

 to the boiler, the bottom of which suddenly dropt out. 

 On examining it, it was discovered to be corroded, and 

 encrusted with a large quantity of strong salt. On this 

 the workings were examinee!, and the springs were 

 found to be confined to a stone drift, that had been 

 driven 200 yards in a north-east direction into the 

 mine. No trace of it is detected any where else, though 

 the pit, and every other near it, have been excavated, 

 both above and below it many fathoms. The depth of 

 the spring is alxmt Ja() yards. It is conveyed to the 

 bottom of the pit, whence it is raised by the colliery 

 steam-engine. The spring has never been known to 

 vary, and is as strong now as when first discovered. 

 About 1 100 tons of salt are made annually. It produ- 

 ces about '20,000 gallons per day, which is four times 

 stronger than any sea water. At Dutterby, near Our- ^j; nc 

 ham, in the bed of the river Wear, is a spaw, arising tcrs _ 

 from a spring of water, strongly impregnated with salt 

 and sulphur. From the circumstance of its being mix- 

 ed with the fresh water of the river, it is difficult to 

 ascertain what quantity of salt it holds in solution; but, 

 on several trials, it has produced double the quantity 

 obtained from sea-water. It is much resorted to for its 

 medical qualities. Doresdale spaw is sulphureous : it 



