Description of a Portable Chamber Blast -Furnace. 167 



furnace. It is composed of three parts, all made out of the 

 coniuioii thiu black-lead melting-pots sold in London tor 

 the use of the goldsmiths. The lower piece, A, is the 

 bottom of one of these pots cut off so low as only to leave 

 3. cavity of about one inch, and ground smooth, above and 

 below. The outside diameter over the top is 5Jr inches. The 

 middle piece or fireplace, B, is a larger portion of a similar 

 {)ot with a cavity about six inches deep, and measuring j\ 

 inches over tlie top, outside diameter, and perforated with 

 fiix blast-holes at the bottom. These two pots are all that 

 are essentially necessary to the furnace for most operations : 

 but when it is wished to heap up fuel over the top of a cru- 

 cible contained within, and especially to protect the eyes 

 i'rom the intolerable dazzle of the fire when in full heat, an 

 upper pot, C, is added, of the same dimensions as the mid- 

 dle one, and with a large side opening cut out to allow an 

 exit to the SJiioke and flame. It has also an iron stem with 

 a wooden handle (an old chisel will do very well), to lift it 

 ofF and on. 



The bellows (which are double) are firmly fixed, by a 

 little contrivance which will take off" and on, to a heavy 

 stool, as is represented in the platej and their handle should 

 be lengthened, to make them work easier to the hand. To 

 increase their force on particular occasions, a plate of lead 

 may be tied on the wood of the upper flap. The nozzle is 

 received into a hole in the pot A, which conducts the blast 

 into its cavity. From hence .the air passes into the lire- 

 place, B, through six holes, of the size of a large gimlet, 

 drilled at cquaF distances through the bottom of the pot, 

 and all converging in an inward direction, so that, if pro- 

 longed, they would meet about the centre of the upper part 

 ^f the fire. The larger hole through the middle of the bot- 

 tom of the same pot is for another purpose. Fig. 3, is a 

 plan of the. same, showing the distribution of these holes. 



As a stand or support for the crucible, I have found no 

 method so good as to fit an earthen stopper into the bottom 

 of the pot B, through the large centre hole which is made 

 for this purjfose. This keeps the crucible in its proper 

 place, in stininj down the coals and managing the fuel. 

 These stoppers are made with great ease and expedition out 

 of the soft red fire-brick sold m London. A piece of this 

 Jjrick, made to revolve a few times within a portion of iron or 

 tarthenware tul)e, presently takes the form of its cavity, and 

 comes out a verv neat portion of cylinder or cone, according 

 to the shape of the tube, fnmi which the stoppers may rea- 

 <JiJv be fashioned. Fisr. 4. represents one of tliese stopper*, 

 L 4 which 



