Page:Popular Science Monthly Volume 60.djvu/145

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THE NATIONAL PHYSICAL LABORATORY.

the Reichsanstalt. Specialized schools for the training of young mechanics in the scientific side of their calling have been formed and now the majority of the leading firms retain in their permanent service one or more trained mathematicians or physicists. In this way again the importance of science to industry is recognized. I have thus noted very briefly some of the ways in which science has become identified with trade in Germany, and have indicated some of the investigations by which the staff of the Reichsanstalt and others have advanced manufactures and commerce.

Let us turn now to the other side, to some of the problems which remain unsolved, to the work which our laboratory is to do and by doing which it will realize the aims of its founders. The microscopic examination of metals was begun by Sorby in 1864. Since that date many distinguished experimenters, Andrews, Arnold, Ewing, Martens, Osmond, Roberts-Austen, Stead and others have added much to our knowledge. I am indebted to Sir W. Roberts-Austen for the slides which I am about to show you to illustrate some of the points arrived at. Professor Ewing a year ago laid before the Royal Institution the results of the experiment of Mr. Rosenhain and himself. This microscopic work has revealed to us the fact that steel must be regarded as a crystallized igneous rock. Moreover, it is capable at temperatures far below its melting point of altering its structure completely, and its mechanical and magnetic properties are intimately related to its structure. The chemical constitution of the steel may be unaltered, the amounts of carbon, silicon, manganese, etc., in the different forms remain the same, but the structure changes, and with it the properties of the steel. The figure on page 136 represents sections of the same steel polished and etched after various treatments.

PSM V60 D145 Section of bad railroad rail.png
Section of Bad Rail.

The steel is a highly carbonized form, containing 1.5 per cent, of carbon. If it be cooled down from the liquid state, the temperature being read by the deflexion of a galvanometer needle in circuit with a