970 IRON 



the throat, or by lateral openings through tho walls into a chamber surrounding the 

 top of the furnace, can be adopted without more or less injury to its action ; and that 

 tho only unobjectionable mode would be to take tho gases from a chamber above the 

 surface of tho minerals, thus equalising the pressure on the whole sectional area of 

 tho mouth, and thereby allowing an equally free flow for tho ascending current up 

 the middle, as well as up the sides of tho furnace. By this method the whole of the 

 waste gases would become utilised, instead of a portion only, and the furnace would 

 be restored to its original state, inasmuch as the direction of the flow of heated gases 

 -would not be interfered with by unequal resistance. To form this chamber, the fur- 

 nace must be covered in, and fed through a hopper, a plan long adopted at the Codner 

 Park Iron "Works, with the supposed advantage of scattering the minerals around the 

 sides of the furnace, and preventing their accumulating in tho centre : a conical charger 

 of this description, but fixed in the throat of the blast-furnace, was in use at the 

 Cyfartha Works more than half a century ago, the minerals being thrown by 

 baskets to the centre of the cone, and allowed to roll down to tho sides of the furn;ico, 

 thus giving a cup form to the surface of the minerals, the larger lumps of course 

 rolling to the centre, and affording a freer passage in that direction for the upward 

 current. It was not, however, until January 1351, that a trial was made, at the 

 Ebbw Vale Works, of an apparatus of this description for collecting the gases. It 

 was then supplied to one of the old forms of conical furnace with a narrow top, and 

 the trial proved eminently successful, the furnace producing any quantity of iron re- 

 quired according to the burden, as usual. Several other furnaces were similarly fur- 

 nished in and around the neighbourhood, and it was now thought that the principle of 

 taking off the gases from a chamber above the surface of the minerals, together with 

 the conical mode of charging, were the only indispensable conditions to success for all 

 furnaces ; and some even which were originally built too narrow at tho mouth were 

 actually improved by the new method of charging, which did not allow of the sur- 

 faces of the minerals rising higher than about 6 feet from the top ; thus giving to the 

 furnace a diminished height, and, as a consequence of its conical shape, a wider 

 mouth. Further experience, however, demonstrated the fallacy of this general con- 

 clusion. 



A large domed furnace was furnished with the same kind of charging-apparatus 

 which proved so successful in former instances ; but, to the astonishment of all, it 

 turned out a complete failure, the same derangements 'occurring as in the former 

 cases, where a portion only of the gases was collected, by sinking a tube into the 

 throat. Now this furnace could not be filled to within 6 or 7 feet of the top, and at 

 that depth the diameter was 13 feet 6 inches, owing to the sharp sweep of the dome ; 

 the actual working furnace was therefore 37 feet high, instead of 44 feet, with a 

 mouth 13 feet 6 inches, instead of 8 feet; and as the minerals cannot lie so close 

 against the smooth sides of the walls as they do locked in each other in the more 

 central region of the furnace, a much freer discharge of the gases up the sides must 

 take place ; and on boring a hole through the side of the furnace, in tho neighbour- 

 hood of the boshes, it was found that, 2 feet in, tho coke and other minerals were at 

 a white heat, but a little further on towards the centre, lumps of black blazing coal 

 were found, with ironstone which had not oven attained a red heat. The charging- 

 apparatus was now raised with the furnace 5 feet, and the minerals drawn up an 

 inclined plane to the charging-cup, thus enabling it to be kept full to within a short 

 distance of the old mouth, after which the furnace worked as usual. That diminished 

 height was not the cause of the bad working of the furnace was afterwards proved, 

 the furnace having been blown out for repairs, and re-lined with brickwork, giving it 

 that form and proportion deemed necessary from the experience gained ; the height 

 being now only 37 feet instead of 44, and the diameter of the mouth 7 foot 6 inches, 

 or one-half of that of the boshes. The same charging-apparatus which failed before, 

 mounted 6 feet above tho mouth, was used, and tho furnace has now been working 

 uninterruptedly for five years, turning out as much as 160 tons of grey pig-iron per 

 week, or, when burdened for white-iron, 200 tons ; economising tho whole of its gas, 

 and as much under the control of the manager as any furnace, either closed-top or 

 open-top, can reasonably be expected to be. It is clear, therefore, that tho covering 

 of the top has nothing whatever to do with tho action of a furnace kept full to tho 

 mouth, and having the proper form and proportions from that point downwards. Tho 

 mouth must be understood to be that part of tho furnaco which represents tho moan 

 height of tho surface of the minerals, and not tho top of tho masonry, and the question 

 arises, what proportion should that bear in diameter to the boshes or widest part, 

 and what the latter should be with reference to height in order to secure a maximum 

 economical effect on tho quality of the iron made, and on the yield of fuel. This state 

 of perfection can exist only when tho isothermal lines in tho furnaco aro parallel t.o 

 the horizon. The temperature of the minerals at any given height above tho tuyeres 



