IRON MANUFACTURE 401 Henderson used a mixture of fluoride of cal- cium or fluor spar and titaniferous iron ore for the purification of pig iron, with good effect. It is impassible to say whether the fluorine exerts any direct action on the phosphorus, or whether the effect is due simply to the lime present in a highly fusible compound. When the balls of soft iron are ready in the puddling furnace, they are taken directly to the ham- mer or squeezer. The trip hammers formerly employed are now generally replaced by steam hammers, which are more efficient and man- ageable. Squeezers are now very generally used for the first treatment of the pud- dled ball. The form gen- erally used in the United States is Burden's rotary squeezer. Fig. 6 shows a horizontal section, different in construction, but on the same principle as the Burden squeezer. The revolving corrugated cylinder is excentric to the frame in which it turns, and the ball in obtained which will combine the properties of all the varieties used. Thus it is customary, in making piles for rails, to put a granular iron on the top and a fibrous iron in the body, so that the finished rail shall have a hard wearing surface and a tough web and flange. Smooth FIG. 6. its passage is considerably condensed, while a large part of its cinder is expelled. From the hammer or squeezer, the bloom is taken while still hot to the rolls, where it is passed through a number of grooves, and formed into a slab or bar, called puddled or muck bar. This is still rough, and must be reheat- ed and again rolled before it is ready for the market. The muck bar is generally broken up in lengths of two or three feet, made into a pile, and raised to a welding heat in a rever- beratory or gas furnace. This white-hot pile <is put through another set of rolls and grad- ually reduced in size until it forms merchant bar iron. The more iron is worked in this way within certain limits, the more homoge- neous it becomes. Fig. 7 shows a merchant train of three high rolls with grooves of differ- ent shapes and sizes. The most varied forms of iron are made by means of rolls or with appropriately shaped grooves. By piling iron of different qualities a finished product may be Fio. 7. rolls are used for making plates and sheet iron. These rolls are provided with a mechanism by which they can be approximated after each pass of the metal. The limits of dimensions within which iron may be worked are very great. Sheet iron has been rolled out to the thinness of the finest paper, and armor plates have been made over a foot in thickness and weighing 33 tons. The operation of puddling is extremely laborious, requiring great muscu- lar strength and endurance. Many attempts have been made to substitute machine for hand labor in this process, with but partial success. The mechanical puddlers, so called, are mostly contrivances by which the rabble can be moved about in the furnace with merely the guidance of the workman. These machines, although they have worked well, have never come into general use. Another similar contrivance is the revolving rabble. This is extremely sim- ple and requires no expensive machinery; it is said to give good results. Richardson's pro- cess consisted in blowing air through a hollow rabble, which was moved about the hearth. The process of oxidation here, as in the Bes- semer process, proceeded rapidly ; the iron soon came to nature, and the manual labor was confined to the operation of balling. Not- withstanding its apparent success, this process is nowhere in use at present. Attention was early directed to the construction of rotary or oscillating puddling furnaces ; but the insuper- able difficulty encountered was the formation of a lining that would stand the scouring effect of the metal. This difficulty has been over- come by Mr. Samuel Banks of Cincinnati, who has constructed and introduced the first prac- tical and efficient rotary puddler. It consists of a revolving chamber, fire grate, and mov- able head piece communicating with the flue. The puddling chamber, 5 to 6 ft. in diameter and 3 to 4 ft. long, is made of two end pieces banded with wrought iron, and provided with detachable rings on the part most exposed to the fire. They rest on carrying rollers, permit- ting free rotation. The two ends are con-
