The accompanying engravings, which we take from _Iron_, give plan and section of the puddling apparatus invented by Mr. Oestlund, as used at the Finspong Ironworks. The gas generator, A, is of the common Swedish type, as used for charcoal. The tube, _k_, conducts the gases into the refining pot, _a_. This pot has a lining of refinery slag, which is melted, as the apparatus revolves, to get it to adhere to the sides. The revolution of the pot, _a_, on its axis, _d_, is effected by the action of the beveled wheels, _b_ and _b'_, and the pulley, _c_, which takes from an iron chain the power given off by a turbine. The spindle, _d_, is supported in the bearings, _e_ and _e', c_ carrying a pair of trunnions which form the axis of oscillation, and allow the apparatus to rise or fall, the whole of this mechanism being supported on the plummer blocks, _f f_. One of the trunnions, _e''_, is prolonged so as to form the axis of the beveled wheel, _b_, and the pulley, _c_, the latter sliding along the trunnion so as to put _b_ in or out of gear. The bush, _e_ is tied by means of the stay, _g'_ to the upper end of the toothed segment, _g_, the lower extremity of which is connected with the second bush at the end of the spindle. By means of the pinion, _h_, revolving on standards, _i i_, and the segmental rack, _g_, the pot can be raised or lowered without interfering with the action of the beveled wheels. [Illustration: APPARATUS FOR MECHANICAL PUDDLING.] The gas from the generator is brought to the mouth of the pot by the tubes, _k_ and _m_. The air necessary for the combustion of the gas is brought in by a tube, _l_, branching from the air main, _l''_. The air tube, _l_, passes into the gas tube and is continued concentrically within the latter. The gas and air tubes both have joints at _m'_ and _m''_. By means of the bar, _n_, which has a counterpoise to keep the moving parts in position, the tubes can be brought from or toward the mouth of the pot, so as to make it free of access to the workman. With a key fitting on the stem, _n'_, the tubes can be turned in _m'_, so as to give the currents of gas and air a more or less oblique direction. To screen the workmen from the heat of the pot a disk of iron, _o_, lined with fire clay on the side next the pot, is fitted to the end of the tubes. [Illustration: APPARATUS FOR MECHANICAL PUDDLING.] Before running the metal into the pot, the latter must be heated, to such a degree that the slag lining is pasty or semi-fluid at its surface. Generally an hour and a half will be spent in heating with gas to this point. There should be sufficient live coal in the pot when the gas is first let in to keep up its combustion; should it be extinguished by excess of air or gas, it must be relit. As soon as the pot begins to get red hot the full heat can be put on.