During the twelve years which have elapsed, since the First Edition of this book was issued, changes which are little short of marvellous have taken place in connection with the metallurgy of iron and steel. In the direction of production, the iron resources of North America have been so developed, and the method of transporting and utilising the materials so improved, that the United States has become the chief iron producing country of the world. The better utilisation of blast-furnace gases, and the use of large gas engines, have transformed many large British and German iron works; while the applications of electricity have opened up a wonderful field for inventive skill. On the theoretical side the advances have been no less remarkable. The application of accurate pyrometers has enabled the metallurgist, with the assistance of the physical chemist, to determine the equilibrium of the iron carbon, and other systems while the application of similar methods has wonderfully extended our knowledge of the properties and constitution of slags. The micro scope, too, has been applied to cast iron, and to other metals and alloys, either as an aid to the pyrometer, or to the chemical analysis, and has opened up a new world to the skilled observer.