Yol. 50.] ANNIVERSARY ADDRESS OF THE PRESIDENT. 55 



Directors with the investigation of that district, and the admirable 

 map of the Harz^ subsequently published by the Survey, was mainly 

 his work. 



Lossen's researches in the Harz caused a new departure in petro- 

 graphy, and he is regarded as the founder of ' dynamo-meta- 

 morphism,' which treats of the effects of mechanical force on the 

 structure of rocks. He supplied evidence of differentiation in rock- 

 magmas, being particular in the determination of rocks according 

 to their structural and chemical characters with reference to their 

 mode of occurrence, whilst he studied the various results of the 

 consolidation of one and the same magma under various conditions. 

 He was not a voluminous writer, but his communications were 

 careful and elaborate. Most of his publications are to be found in 

 the ' Jahrbuch der konigl. Preussischen geologischen Landesanstalt 

 und Bergakademie,' in the volumes of the German Geological 

 Society, and in the Proceedings of the ' Gesellschaft der natur- 

 forschenden Freunde.' Though terribly afflicted with deafness, 

 which precluded him from general conversation, Prof. Lossen was 

 well able, through his exceptional command of language, to carry all 

 before him when a suitable occasion arose. 



He died at Berlin, after a long and painful illness, on the 24th 

 February, 1893, at the age of 52. 



Dionys Stttr, Foreign Member, was born on April 5th, 1827, 

 at Beczko, in Upper Hungary, at which place his father was 

 schoolmaster. After completing his classical studies at the 

 Gymnasium ( = Grammar School) at Modern, and his course of 

 philosophy at the Protestant College at Pressburg, Stur attended 

 the mathematical and physical classes at the Vienna Polyteeh- 

 nikum, and subsequently the public lectures on mineralogy 

 and geognosy, which were delivered in the later 'forties at the 

 Imperial-Royal Museum of Mines by Herren von Haidinger, von 

 Hauer, etc. He perfected his professional training at the Imperial- 

 Royal Mining Academy in Schemnitz. 



Thoroughly prepared in this wise for the calling of a field- 

 geologist, and well endowed in body as in mind, Stur joined, in 

 April 1850, the then newly-established Imperial-Royal Geological 

 Survey, on the staff of which he served uninterruptedly for well- 

 nigh 43 years, during the last seven of which he was Director, 

 being further honoured with the title and office of Councillor of the 

 Imperial-Royal Court. 



For twenty-five years Stur took a very prominent share in the 



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