SODA.— Black-asii Balls. 809

between the bridges being fitted up with brickbats,clinkers, or the like.

In the majority of works the fire gases, afterhaving been used under or over the boiling-downpans, are carried away, as in Plate III., into a flueleading to the chimney, and provided with a damperfor the regulation of the draught; but as theypossess a considerable degree of heat, it is mostadvisable, where there is space, to utilize them stillfurther. This can be done in various ways; onewhich commends itself very much is to conduct theescaping gas over the settlers for “ tank-liquor,”which must for this purpose be long (say old steam-boilers cut in two) and covered over by an arch;in that case they not only communicate to the set-tled tank liquor a preparatory heat before it is runinto the pans, but they will leave behind with it agreat portion of the mechanically carried away par-ticles of liquor and salts from the pans. This does notamount to very much, but it mounts up in the longrun to something worth saving. As the settlers fortank liquor are in any case placed in such an eleva-tion as to be able to run into the pans therefrom,there should be no great difficulty about it, especiallywhere the chimney stands on a bank at a higher ele-vation, which is very usual on the Tyne. Theescaping heat may also be used for warming thewater used for lixiviating the tanks.

In all cases, even where the fire only heats oneboiling-down pan, ball - furnaces require a gooddraught to work properly, and they are thereforemostly connected with tall chimneys, from 100 feetupwards. The writer succeeded in increasing theoutput of several ball-furnaces by 50 per cent, byabolishing their chimneys of 40 feet height, one foreach furnace, and substituting for them one commonchimney of 130 feet height.

The balling operation in the furnace describedabove is carried on in the following manner:—Whenthe furnace has been heated up sufficiently (whichtakes at the week-end, after a “ damp-up,” only fiveor six hours; but in the case of a “ cold heat-up,”perhaps twenty-four' hours)—viz., to a bright redheat—the charge of sulphate of soda, carbonate oflime, and coals is put into the back bed, eitherthrough the working door, or preferably by droppingit in from the top through a hopper. In the regularcourse of work this charging is done when the ballon the working bed is about half finished; andwhilst it is entirely finished, the new charge on theback bed'obtains a preparatory heating. After theball on the working bed has been drawn into the“ bogie,” the furnace is allowed to go empty forfive minutes, or even longer, to heat the front bedthoroughly; and only then the new charge istransferred from the back bed to the working bed,principally by means of an oar-shaped tool, called“ slice ” in Lancashire , or “ paddle ” on the Tyne.The paddle head is in this case preferably of castiron, about 24 inches long, 5 inches wide, and five-eighths of an inch thick. On the Tyne it is very usualto “ split ” the ball—that is, to move in the firstinstance only about two-thirds of the ball-mixtureVOL. II.

from the back bed to the front bed, in order to getmore heating surface and easier work whilst themixture is still rough. The portion brought on tothe working bed is well spread out upon it, andmoved towards the fire-bridge, where the heat isgreatest. It must be well turned over, so as toexpose every part of it to the action of the flame,and the “ paddle ” or “slice ” plays here the greatestpart still; the parts softened by the action of thefire are turned down, and fresh surfaces are turnedup. This turning over has to be repeated abouttwice; and as soon as the charge begins to soften,the remainder of the mixture is worked down intoit from the back bed. In between the turnings-over the working door is let down, and the furnacefire is allowed free action on the charge for severalminutes. After the whole has been thoroughlysoftened, the workman must keep uninterruptedlyat the work, because the critical time has come. Hemust therefore continue turning the mass over andover with the paddle. It becomes in this stagealmost liquid all over, but it would be very wrongto draw it just yet; the “paddling” must be con-tinued, and after a few minutes the mass becomesmuch stiller. The coal contained in it' is nowmostly consumed. It is now time to “ rake ” theball. The workman, without any interruption, takesdown his rake (with cast-iron head), and thoroughlyworks up the mass, mixing it up as equally aspossible, and working it all the time towards thedoor. His tools, which weigh about half a cwt.each, are supported by the horizontal bars shownin Plate III. in front of the doors. Before usingthe rake, these bars and the rake-shank are allgreased with cart grease. There is besides a chainwith a hook at its end hanging dow T n from therafters in front of the furnace, which enables thefurnaceman to rest the fore-end of his tool as well,and materially lightens his actual exertion. Every-thing now depends upon the judgment of thefurnaceman. As soon as he thinks that the ball isquite stiff enough, and before it has had time to gofurther and to be “ burnt,” he pulls it, by means ofhis rake, out into the “ bogie ” or “ pot,” which hasbeen beforehand placed in front of the workingdoor. Only just before the raking out, jets offlame, caused by carbonic oxide, and burning with ayellow sodium flame, appear in the mass; these arecalled “ candles ” in Lancashire , “ pipes ” on theTyne, and they should burst out equally all overthe ball while it is being and after it has beendrawn, and a practised eye judges from theirregular appearance whether the ball has been wellmade. The latter is well stirred up and mixed inthe bogie itself, and ought to swell up and rise inthe same; the action seems indeed to go on eventhen, and to continue till the ball is cooled down.It is allowed to cool and solidify till just before thenext ball is ready for the final raking, when the oldball is wheeled away, tilted out of the bogie, andthe latter wheeled back to the furnace to receivethe new ball.

There is very little difference in the appearances102