662 Mr. Richard T. Glazebrooh [May 24, 



nearly all the glass required was of home manufacture. Very shortly 

 afterwards an export trade in raw glass began, which in 1898 was 

 worth 30,000Z. per annum, while the value of optical instruments, 

 such as telescopes, field-glasses and the like, exported that year was 

 250,000Z. Such are the results of the application of science, i. e. 

 organised common sense, to a great industry. The National Physical 

 Laboratory aims at doing the like for England. 



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 manufactui'es 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 realise 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 \V. 

 Roberts-Austen for tho 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 experiments of 

 Mr, Rosenhain and himself. 



This microscopic work has revealed to us the fact that steel must 

 be regarded as a crystallised 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, &c, in the 

 different forms remain the same, but the structure changes, and with 

 it the properties of the steel. 



Sections of the same steel polished and etched after various treat- 

 ments show striking differences. Eor instance, if a highly carburised 

 form containing 1 ■ 5 per cent, of carbon be cooled down from the 

 liquid state, the temperature being read by the deflection of a gal- 

 vanometer needle in circuit with a thermopile, the galvanometer 

 shows a slowly falling temperature till we reach 1380° C, when 

 solidification takes place ; the changes which now go on take place 

 in solid metal. After a time the temperature again falls until we 

 reach 680°, when there is an evolution of heat ; had the steel been 

 free from carbon there would have been evolution of heat at 895° and 

 again at 766°. Now throughout the cooling, molecular changes are 

 going on in the steel. By quenching the steel suddenly at any 

 given temperature we can check the change and examine micro- 

 scopically the structure of the steel at the temperature at which it 

 was checked. 



[Slides were shown representing the microscopic structures of 

 steels subjected to different treatment as regards temperature and 

 annealing.] 









