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try, I will repeat briefly the interesting account given by one 

 of the chemists of the Illinois Steel Co. at a meeting in Chicago. 

 Dr. Cremer told us how after a train had been wrecked by 

 a broken rail, the results of miscrocopic examination of the 

 rail, considered in the light of our physico-chemical knowledge 

 of the conditions of equilibrium of the various components in 

 steel, showed that the upper surface of the rail must have been 

 subjected to a very high temperature and then suddenly cooled, 

 with the result that the surface had been made brittle. Inves- 

 tigation showed then that the locomotive of the preceding train 

 had taken in water in a violent snow storm and that the rail 

 in question had been directly under the fire-box of the engine 

 and when the train moved on, the falling snow prevented the 

 required slow passage of the heated surface through the transi- 

 tion points of steel ; the surface thus became brittle and the 

 impact of the next train broke the rail by starting a fissure in 

 the surface. 



This is only a small instance of the profound change in 

 methods of technical investigation and work which have fol- 

 lowed van"t Hoff's discovery of the laws of solution in the field 

 of pure chemistry. On the other hand, Otto N. Witt, in the 

 course of his work as expert in one of the leading aniline-dye 

 manufacturing houses, in 1876 developed the fundamental 

 points of a theory of the cause of color in organic compounds 

 and the theory of their capacity to form dyes — theories, which, 

 emanating from a technical chemist, have been of profound im- 

 portance in the development of the pure scientific examination 

 of the question, and form even after thirty years the basis for the 

 present views on this subject. In developing for the Badische 

 Anilin-Fabrik the contact process of manufacturing sulphuric 

 acid, a process which is rapidly displacing the older, awkward, 

 lead-chamber process, Knietsch, as he himself explains, was 

 led from the beginning by considerations of pure theoretical 

 chemistry; he was not led by the experience gained and con- 

 clusion reached by applied chemistry ; on the contrary he had 

 sixty years of practical failures and costly disappointments be- 

 fore him in the previous experiments of technical or applied 



