GLASS. 



thirty- fix hours, they fill the c'lderns, which are in the fame liavc not been eye-witnefll-J of that rurpririn» manufat.-- 



furnace, and. which are left there about fix hours lonjjer, turc. 



till fuch time as they appear all white through the excellivc As fall as the cifterns are emptied, they carry thein back 



heat. to the furnace and take frefh ones, which they empty as br- 



To get the cifterns with the metal out of the furnace, fore. Tliistliey continue to do, folonfj as there are a^iy fu!l 



they make ufe of a large iron chain which opens and fhuts cifterns ; laying as marty plates in each carquaiffc a> it will 



with hooks and eye?. From tiie middle of this, on each hold, and Hopping them up witii Joorj of baked earth, or 



fiJe, arife two maflive iron pins, by which, with the afiiflance clay, and every chink witii cement, as foon as thcT ar- 



of puUics, the cifterns arc raifed upon a kind of carriage of full, to let them anneal, and cool again, which requires abou! 



a proper height ; and thus conducted to the table where the fourteen days, 

 glafs is to be run. The ciftcrn is then raifed above the The firll running being difpatched, ther prepare another 



tables with au engine, in form of a cran~ *- — ■ '^ - - ■ ' ■ - 



iron bars, fo contrived as to thro 



pofition, which difchargcs a to: 



with which the table prepared for this purpcfe is prefently 



covered. 



rn is uien rauea aoove uie The firft running being difpatched, ther prepare another . 



jf a crane, by means of two l,^ jip.jng tjij. cifterns anew, from the matter in the oots ; zr.i 



Dw the cifteni into an inchncd after the fccond, a third, and even a fourth time, till the 



an-ent of matter, all on fire, nieltinir nots are quite emptv. 



g pots are quite emptv 

 The cifterns at each running fliouIJ remain at lead 

 fix hours in the furnace to whiten ; and when the firi 

 annealing fi;rnace is full, the cafting table is to be carried 

 to another. It need not here be obfcrved, that the car- 

 quaini's, or annealing furnaces, mull firft have been heat- 

 ed to the degree proper for them. It may be obfervcd, 

 that the oven full, or the quantity of matter commonly 

 prepared, fupphes tlie running of eighteen glades, wliich 

 is performed in eigliteen hours, being an Lour for each 

 glafs. The workmen work fix hours, and are then re- 

 lieved by others. 



When the pots are emptied, they take them out, a) 

 well as the cifterns, to fcrape off what glafs remain?, 

 which otlierwife would grow green by continuance of 

 fire, and fpoil the glafies. They are not filled again in 

 lefs than thirty-fi.>c tiours, fo that they put the matter 

 into the furnace, and begin to run it ever)' fifty-four 

 hours. 



The manncrofheatingthc large furnaces is fingular enough; 

 the two tilors, or perlons employed for that purpofe, ia 

 their ftiirts, run round the furnace without making the lead 

 ftop, with a fpecd fcarce inferior to that of the lightefl 

 courier : as they go along, they take two billets, or piece* 

 of wood, which are cut for the purpofe ; thefe they throvr 

 into the firft tiihirt ; and continuing their courfe do the fan-.e 

 for the fecond. This they hold vnthout interruption for fix 

 hours fucccffively ; after which they are relieved by others, 

 &c. It is furpriling that two fucli fmall pieces of wood, 

 and whicii arc confunicd in an inftant, fiiould keep the fur. 

 nace to the proper degree of iieat ; which is fuch, 

 that a large bar of iron, laid at oik of llie mouths of 

 the furnace, becomes red-hot ia Icli than half a mi- 

 nute. 



It is computed, that a furnace, before it be fit to rut 

 glafs, coils above three tlioiifand lite hundrovl poundi ( 

 that at leaft fix months are required for the building it 

 anew, and three months for the refitting it ; and that 

 when a pot of mattL-r burlU in the fumicc, the lof« of 

 matter and time amoiyits to abov ■ t',v» hundred and Cir.j 

 pounds. 



The glafs, when taken out of the melting-furnace, iieedi 

 iTcjthing farther but to be ground, polifhed, and foIiate«l. 

 But before thefe operations are performed, they cut and 

 fquare the edges of the plates ; which is pcrfonaed witli a 

 rougli diamond, paffed along tlie furface ot the glafj, upon 

 a fquare ruler, like that of the gl.Tziers. and made to cui 

 into the fubltanceof the glafs to a certain depth. This cut 

 operation, is t!ie quickncfs and addrefs wherewith fuch is then opened by gently knocking with a fmall hammer on 

 inafTy cifterns, filled with a flaming ir alter, are taken out of the under fide uf the glafs jutt under it j by which mcan» 

 the furnace, conveved to the table, and poured on it, the the piece comes off, and the ro.ighncfT.s of the edges are re- 



coHcctTabk to fuch as raov.d by pincers The plates are tlii-ii laid bv for _fr.T./)itX. 



T t 2 j-'^/tfiwf. 



The table on whicli the glafs is to be run, is of fmooth 

 thick copper-plate, about ten feet long, and fix feet broad. 

 It is fupported on a wooden frame, with truckles, fur the 

 convenience of removing from one carquaifie, or annealing 

 furnace, to another, in proportion as they are filled. 



Or, when each pot has ii cafting table, it is ilrongly fup- 

 portcd by mafonry, and contiguous to each table on the 

 fame h-vcl are tlie aniuMling oven3, upon which, being flat, 

 the glafs, wlieu caftand I'ufficiently cooled, may be Aid from 

 off the copper-table without much difficulty. Tlie tops of 

 the flat ovens and the tables are on a level with the corre- 

 fpondiig opening of the furnace, whence the cuvettes or 

 cifterns are withdrawn. When the glafs is melted and fined 

 ia the manner rdready ftated under the article Flint Glas.s, 

 the cuvette or cillern, prcviouily made hot in the furnace, is 

 filled out of the pot with a copper ladle, about ten inches in 

 diameter, fixed to an iron handle feven feet long, properly 

 fupported on an iron ftay by tv>-o workmen ; and after re- 

 maining in the furnace for fome hours, till tlie famples taken 

 out for trial appear to be quite clear and limpid, the door of 

 the furnace is opened, and the cuvette is pulled out and re- 

 moved to the fide of the copper table. It is then fcuramcd 

 with an inftrument confifting of a copp..r blade fet in iron, 

 and hcifted for thedifcharge of its contents on the table, in 

 the manner already mentioned. 



To form the thicknefs of a glafs, and to make the fur- 

 face fmooth and even, there are two iron rulers or rims, 

 placed round the edge of the table ; and on thefe reft the 

 two extremes of a kind of roller, orholhnv heavy cyhnder 

 of copper, turned after being cail, and al.'out 500 pounds 

 in weight, whith ferves to drive tlie liquid matter before it 

 to the end of the table, or mould. Tiie iron rulers being 

 moveable, and capable of being fet clofer, or farther apart, 

 at pleafure, determine the width of the glaftes, and retain 

 the matter, that it does not run off' at the edges. The wafte 

 glafs, if any, falls into a veffel of water, and is reiervcd for 

 the next melting. 



As foon as the matter is arrived at the end of the table, 

 jtnd the glafs is come to a confiftenee, examined by the di- 

 rectors of the manufacture, and approved, they (hove it oif 

 into the annealing furnace, with an iron raker, as wide as the 

 table, that has a handle two fathoms long ; being affifted by 

 workmen on the other fide of the carciuaifte, wlio, with iron 

 books, pull the glafs to them, and range it in the carquaiife, 

 v.'hich holds fix large glafies. 



■Wliat is moll furpriling throughout the whole of this 



lul. foread. 



Tlw whole io 



