QUARRY. 



All sere of ground contains - 4S40 fquare yards, 



■ ,\yliich, multiplied by the thicknofs 6 yards, 



p.jyeg ... 29040 cubic yards in 



From which deduft -i,^ for wafte and ^ an acre, 



the p^rtsor pillars necefl'ary to be > 9680 

 loft in working - -J 



there remains igs^ cubic yards to 



. be vvronght. 



And as three cubic yards of coal, when wrought, afford 

 a Newcaltle chaldron, therefore 



19360 = gives 6453 Newcaule chal- 

 drons per acre, 



divided by 3 



The coals exported yearly from the rivers Tyne and 

 Wear, with Hartley and Blylli, amount to about 825,000 

 chaldrons, which, with the home-confumption of the two 

 counties of Northumberland and Durham, will make the 

 quantity of coals raifed yearly about 1,000,000 chaldrons. 



And the chaldrons] ooq^qoo ^ gives 155 acres nearly 

 raifed yearly J ° , , ,■ 



divided by the chal- 

 drons per acre 



per year, cleared of 

 coal fix yards thick. 



'} '^^^^ 



And by ellimating the breadth occupied by the caking 

 coals to be on the average eight miles broad, and twenty-five 

 miles long in the two counties, it is found that there will be 

 about two hundred fquare miles, or 128,000 acres of coal 

 proper for exportation. 



From Nt-wcaltle 510,000 chaldrons. 

 Sunderland 315,000 ditto. 



In all 825,000 

 Then the whole area 128,000 = 825 years. The time 



■ divided by the! before this fpace will 



yearly confump- V 155 be wrought out. 



tion - J 



It is, however, fuggefted, that there are fome reafons to 

 fuppofe that a thicknefs of feam equal to fix yards will not 

 be obtained all over an extent of two hundred fquare miles, 

 probably not more, on an average, than four yards j in 

 which cafe the coal will be exhaulled in five hundred and 

 fifty years. And if the aggregate thicknefs of the feams 

 to be obtained Ihould prove only three yards, then little 

 more than four hundred will be the term of continuance ; 

 but it is probable, it is thought, that before the half of 

 that time be elapfed, the price to theconfumer will be con- 

 fiderably increafed from the increafed expence of obtaining 

 them, and the increafed length of carriage from the pits to 

 the rivers; this lait, it is prefumed, may be reduced in fome 

 fituations, by adopting canals inilead of waggon-ways, 

 which, it has often been wondered at, have never yet been 

 attempted. From this inveftigation, it is fuggefted, that 

 the apprehenfions of exhauftion are not fo chimerical as they 

 have been fuppofed and reprefented to be by lome perfons. 

 Wht..n, however, the vail extent of the worknig and un- 

 wrought trafis, in the different parts of the country, are 

 confidered, there cannot be any grounds for fear, in this 

 rcfpedl, for a vaft length of time yet to come. 



Pits, fome what of the quarry kind, are wrought in one 

 diftrift of th.s country, that of Chefhire, for the raifing of 

 rock fait, in fome of which large quantities of this material 

 are procured, from different depths, and diff^erent thick- 

 neffes of the ftrata of it. In the getting of it diff'erent 

 means are employed, as thofe of blafting, picking with im- 

 plements, for the purpofe of roofing, the ufing of horfes, 

 and machinery wrought by fteam, for forcing up the fub- 



flance, and fome others. The digging, raifing, and work- 

 ing of this article, employs a great number of labourers, and 

 it is of much importance to the county in many points of 

 view. 



But though this fort of material is found in feveral dif. 

 ferent pai-ts of the county, pits, or fliafts of it, are at this 

 time only wrought in the vicinity of the town of North, 

 wich. Tiiis arifes from a great many different caufes, but 

 principally from that of the want of water-carriage for the 

 conveyance of the material from them. The number of 

 pits or fiiafts, which there are at this time in work, for 

 the purpofe of raifing this article, are aVjout a dozen. They 

 are by much the moil commonly made in fomething of the 

 fquare form, being fecurcd on the fides by m.eans of ftrong 

 timber, but they have occafionally a round form, and are 

 walled on the fides with bricks. 



The beds of this material, that are to be raifed, are 

 wrought at various depths, the deepell being in general the 

 moft pure, and they vary equally in their thicknefs and 

 direftions, as iuggeited above. In fome cafes the beds are 

 of the greatell thicknefs, the more they approach the 

 north-eail, decreafing in a gradual manner, in their courfe 

 to the fouth-weil ; and in fome inllances thev inclme from 

 north-weft; to fouth-eaft, dipping at the rate of about three 

 feet in twenty-feven or thirty. 



The ftrata, which are paffed through in getting at and 

 working the rock-falt, lie in a very regular manner, and 

 confift, in general, of a hard clayey fubftance and a fort 

 of gypfeous material in mixture in various ways and pro- 

 portions, that of the latter kind being the moft predomi- 

 nant as the pit or fiiaft approaches the rocky faline fub- 

 ftance. In working, the clayey matter is defignated by 

 the name of metal of the feveral different colours Ijelonging 

 to that fort of fubftance, and the other material by that 

 of plaifler. Tliefe ftrata are moilly of a fohd compaft: 

 nature, but occafionally broken in particular places, when 

 the metal is lermeA Jli/iggy by the workmen. 



In the bufinefs of working the pits, and raifing the rock- 

 falt, the rocky beds are reduced into pieces of proper fizes 

 for the purpofe, by means of blowing them with gun- 

 powder, and thofe of fplitting and dividing them viath ham- 

 mers and proper wedges for fuch ufes ; a good fecure head- 

 way or roofing being conftantly provided in the firft place, 

 to the opening from which the falt-rock is to be taken, 

 which is eff^efted by the ufe of fmall (harp picks, carrying 

 on the work in a plain fimple chambering manner. 



The workings are funk from thefe chamberings to dif- 

 ferent depths, as the nature of the beds of rock, and the 

 quantity of the purer kind of rock-falt, or Prufiian rock, 

 as the workmen term it, may direft ; but commonly about 

 fifteen feet. Occafionally the roofs or headways of the 

 pits or ftiafts are fupported by confiderable fquare pillars 

 difpofed in a fomewhat regular manner, but in other cafes 

 they are wrought out in a fort of long openings, accord- 

 ing as the workmen are inclined. 



In getting the rock-falt, the workmen are paid by the 

 ton at the rate ufually of about two (hillings, they finding 

 the gunpowder and other tools. 



In raifing the fait from the pits or (hafts, horfes were 

 formerly entirely made ufe of, but within thefe few years, 

 recourfe lias been had to the improved fteam-engine, as 

 already noticed, though it is not yet generally employed at 

 every pit. See RocK-SALT, Rock-salt Pits, Salt, and 

 Salt Brine Strings. 



It is evident from the above account, that in whatever 

 way they are confidered, the quarries of different kinds 

 in tlus country are of very material importance to its 



profperity 



