Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/338

 322 IRON Ordinary Furnace. Siemens Furnace. Silica, 11-98 15-36 Ferrous oxide 68-69 66-33 Phosphoric anhydride 14-43 14-28 0-24 0-28 Descriptions of the cost and working of Siemens puddling furnaces in several iron-works are given by the Puddling Committee of the Iron and Steel Institute (Journal, 1872, p. 123). Besides the gases generated from coal, various other kinds of fuel for puddling furnaces are sometimes employed ; thus petroleum and FIG. 34. Witham s Mechanical Rabble. coal tar have been used in American works, as also has the natural. fas from the Pennsylvanian oil wells, and that produced by partially urning damp sawdust (see 10). FIG. 35. Dormoy s Rabble -Transverse Section. 24. Machinery for Saving Labour in Puddling. In order to diminish the amount of laborious and exhausting work performed by the pmddler, various mechanical contri vances have been introduced from time to time, mostly consisting of an ordinary rabble or some similar stirrer to which motion is communicated by machinery, in such a way as to move it (with some amount of guidance on the part of a workman) more or less in the same way as the puddler would use it. Fig. 34 represents one of this class of mechanical rabbles known as Witham s machine rabble applied to a double puddling furnace. Dormoy s rabble (figs. 35, 36) differs from others of this class in being worked by rotation like a hair-brushing machine ; the tool being made to revolve very rapidly (300 to 500 turns per minute for white iron and 800 to 1000 for grey pig) gives the metal such an impulse that it gyrates horizontally round the bed, con tinually renewing the surface in contact with the atmosphere ; this is further aided by making the end of the rabble to carry a disk, which is replaced by a short twisted point when the metal comes to nature ; only for the final balling is a hand-worked rabble re quisite. According to Paget (Journal I. and S. List., 1872, 338) one fettling serves for forty charges worked in this way ; an in crease of 30 per cent, in the yield is effected, with an expenditure of only G 552 parts of coal per unit of wrought iron made (11 4 cwts. per ton); the puddler is but little fatigued, although charges are worked off much more rapidly, whilst sulphur and phosphorus are so well elimi nated that inferior brands of pig produce iron equal to good charcoal iron. Numerous other mechanical rabbles and analogous appliances have been introduced by various FIG. 36. Dormoy s Rabble Details of Puddling Tool. inventors ; reports on the working of several of these (Witham s, Griffith s, Stoker s, Wilson s, &c.), and on the construction and performance of several kinds of puddling furnace, are given by the Puddling Committee of the Iron and Steel Institute in the Journal, 1872; also of the Carron-Dormoy furnace and mechanical rabble, ibid., 1876, 109. Many attempts were made prior to 1869, chiefly by Walker and Warren, Maudsley, Yates, Tooth, and Menelaus, to effect puddling by a revolving furnace rotated by machinery so as to cause the requisite intermixture of