Defcript'ion aj a Three-hlajl Fajhig Furnace. y^ 



may be pulled by the fame perfon who manages the fire of 

 the furnace, which in certain cafes is iieceflary. 



The tuyeres of forged iron which receive the ends of the 

 copper tubes are fecured in their proper apertures in the cir- 

 cumference of the furnace by pieces of brick and mortar 

 fimilar to that employed for filling up the joints; and the 

 ends of the copper pipes introduced into thefe tuyeres are 

 luted with the fame mortar, a little thickened with brick-duft. 



The aperture of thefe tuyeres towards the interior of the 

 furnace is only nine lines in diameter ; on which account, as 

 the volume of air furnifhed bv the bellows cannot pafs fo 

 quick as it is produced, it becomes condenfed in the box 

 placed above the cocks. By thefe means a very uniform blaft 

 IS obtained, which can alfo be regulated by opening more or 

 fewer of the cocks. 



During more than fix years, fince this furnace was con- 

 ftrutted, it has fuffered no derangement: it is not even 

 cracked. It is however worn in the inlide by the violence of 

 the heat it has experienced, which has increafed its diameter 

 about two inches. The parts round the three tiiveres have 

 a!fo got hollowed, fo that it has need of being repaired. It 

 is intended to make it deeper, and to have a kind of move- 

 able muff's or linings made of fire-clay, in order that its dia- 

 meter may be reduced at pleafure"^ it is meant alfo to con- 

 flrucl it in fuch a manner, as to depofit the red or fupport for 

 the crucible, not on the bottom of the furnace, but on bars 

 of forged iron placed at the diftance of fome Inches from that 

 bottom, fj as to leave below them a vacuity in which the 

 biall of the bellows may be difuifed, and from which it may 

 rife, paifing between the bars to traverfe the mafs of charcoal 

 which furrounds the crucible. The blall will then produce a 

 more uniform fire, and the flame can no longe^be direfted 

 againd the fides of the crucibles; fo that the riik of their 

 breaking by hidden inequalities in the heat will be much lefs. 



This alteration is going to be iunnediately carried into ex- 

 ecution, and the method propofed for doing it is as follows: 



A round frame will be made of forged iron, in which 

 bricks will be placed in the fame manner as above defcribcd. 

 In the lower part of the furnace an aperture will be refervcd 

 for raking out the aflias, which will be doled by means of 

 a door of baked earth carefidly luted with clay. Some inches 

 above the bottom of the furnace will be placed a grate of 

 forged iron, and between this grate and the bottom of the 

 furnace tiie tuyeres will tirminate, and the blad he intro- 

 duced. Wuflfs or linings of very icfratlory earth will Uieii 



be 



