Seamless tubes are easily bent, swaged, upset, spun or otherwise changed in form, as the material is ductile and there are no welds to open. Very large tubes are not made in the way just described. They are rather made by “cupping” flat, round steel plates through a die. A cup is then in several successive drawings put through smaller dies, under which treatment it grows longer each time and gets a thinner wall until it has become a long tube with the one end still closed. For open ended tubes this and the upper, open end are cut or trimmed off. Cold-drawing here necessitates annealing to restore ductility just as it does elsewhere and each annealing operation is necessarily followed by pickling for removal of the scale formed. By rapidly spinning large tubes in lathes or other machines and the application of pressure with the proper tools and lubrication, the walls of the tubes may be deformed. In this way the ends may be expanded, made smaller, or completely closed. By such “spinning” operations large tubes are made into articles of various shapes. By this same “cupping” or hydraulic drawing of flat, well lubricated sheets of soft steel, seamless high-pressure gas cylinders, steel drums, barrels, and the like are made. CHAPTER XXII TRANSFORMATIONS AND STRUCTURES OF THE STEELS It was “Ali Baba” who is quoted as saying, “Those who do not know how to take the Philistine, better hadn’t!” or words to that effect. Now through these chapters we have attempted to discuss in an entirely non-technical manner the subjects presented. On this account we were compelled to forego discussion of many things which are highly important and interesting but which are more or less difficult of explanation without the use of scientific terms and theories. One such has been the “mechanism” of the hardening of steel and its opposite, its softening by annealing. For those who may desire to get a glimpse into this “wonderland” it is hardly fair to refrain from brief discussion of the subject just because it is technical and difficult and so may prove to be tedious to some who have little reason to be interested. It seems desirable, therefore, to impose this more technical chapter or two that the subject of the real metallurgy of iron and the steels may at least be “hinted at.” We say “hinted at” advisedly for it is a long, long story, and, even now, after a great many years of serious study no one has yet read it to the end. We are not saying this in a discouraging way, however, for there seems little reason to doubt that the multitude of facts which have been disclosed through the tireless experiments and the study of hundreds of investigators have put us well on our way to the solution of this one of Nature’s great problems.