to organize his scientific society in spite of serious opposition from the Austrian police. Haidinger, founder and president of the "Freunde der Naturwissenschaften in Wien" undertook to publish its proceedings from 1840 to 1850. The last meeting of the "Freunde der Naturwissenschaften in Wien" took place on 29 November 1850. After that the learned society ceased to exist. In addition to his work on the collections of the mineralogical museum, his lectures on mineralogy and geology to young mining engineers, Wilhem Haidinger found the time to continue his own research and published some 105 papers during the years 1849 to 1860. Dolomitization Haidinger's scientific work became more and more concentrated on the phenomenon of "pseudomorphosis": that is minerals which have taken up the outer aspect of another mineral. For example, anhydrite would have changed into gypsum, but the original cleavage planes and crystal habitus would give the impression of anhydrite. Another example given by Haidinger was that of calcium carbonate, which would readily change into calcium magnesium carbonate (dolomite). In his own words: "... part of the carbonate of lime is replaced by carbonate of magnesia, so as to form in the new species a compound of one atom each. How this change was brought about, is a difficult question to resolve, though the fact cannot be doubted, as we have in the specimen described a demonstration of it, approaching in certainty almost to ocular evidence". To geologists Haidinger is known especially for his postulate of the "dolomitization" reaction that would change calcium carbonate into dolomite at low temperatures (below 100 degrees Celsius). A solution of magnesium sulfate would convert calcium carbonate into dolomite plus calcium sulfate in solution. Nonetheless, in 1844 Haidinger related how his friends, the well-known chemists Friedrich Wöhler, Eilhard Mitscherlich, and Leopold Gmelin had explained to him, that powdered dolomite will react, even at room temperature, with a solution of calcium sulfate to give calcium carbonate plus a solution of magnesium sulfate. ("Durch meinem verehrten Freund Wöhler wurde ich auf die Beobachtung, die auch Mitscherlich und L. Gmelin anführen, aufmerksam gemacht, daß man Dolomit in Pulverform künstlich zerlegen kann, wenn man eine Auflösung von Gyps durch denselben dringen läßt. Bittersalz wird gebildet und kohlensaurer Kalk bleibt zurück. Dieser Versuch erläutert wohle mit hinreichender Evidenz die Bildung des Kalkspathes aus Dolomit bei unserer gewöhnlichen Temperatur und atmosphärischer Pressung": Haidinger, 1844, p. 250.) It was Haidinger's employee at